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A LABORATORY GUIDE 
' FOR BEGINNERS IN 
ZOOLOGY 



BY 

CLARENCE MOORES WEED, D.Sc. 

AND 

RALPH WALLACE CROSSMAN, A.B., M.Sc. 



t i 



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BOSTON, U.S.A. 

D. C HEATH & CO, PUBLISHERS 

1902 






THE LIBRARY OF 

CONGRESS, 
Two Cowsfi Received 

SEP. 26 1902 

COPVRWHT ENTWV 

CLASS <^XXo No. 
CO** s 



Copyright, 1902, 

By CLARENCE M. WEED 

and RALPH W. CROSSMAN. 



Plimpton press 



H. M. PLIMPTON &. CO.. PRINTEPS & BINDcRS, 
NORWOOD, MASS., USA. 



PREFACE 

It is generally conceded that a satisfactory course in 
zoology requires both laboratory study of animal forms 
and lecture or text-book presentation of the laws of animal 
life. The teachers most conversant with pedagogical 
principles also contend that the greatest educational value 
Qf the subject lies in the opportunity it gives to furnish 
the student with an adequate first-hand knowledge of 
organic evolution. To accomplish this a course in which 
the pupil begins with the lower forms and works gradually 
upward is necessary. For the pupil thus follows the de- 
velopment of living things, seeing how each succeeding 
form is an improvement over the one that went before, 
and getting some idea of the great laws which govern the 
growth and sequence of animal life. 

In his study of these forms of life the pupil needs a 
guide which shall lead him wisely without telling him too 
much, and which shall stimulate him to see and to think 
without bewildering him with questions that he cannot 
answer. In this little book such an attempt is made. 
Since the directions were first used in my own classes 
some ten years ago modifications have been made every 
year, until in their present form I have found them thor- 
oughly workable with average classes of beginners in 
zoology. 



iv Preface 

The directions in the introductory chapter are designed 
to help the teacher in getting material for study; they are 
not intended for the pupil, although the figures should be 
helpful in enabling the teacher to show the class what to 
look for in the case of the microscopic specimens. 

In the preparation of a few of the chapters valuable 
assistance has been rendered by Mr. Albert F. Conradi, 
while the drawings have been made by Mr. Robert A. 
Cushman. The authors are also under great obligations 
to Professor J. H. Gerould of Dartmouth College, who has 
kindly read the proof, and made many valuable sugges- 
tions for the improvement of the Guide. 

C. M. W. 

New Hampshire College of 

Agriculture and Mechanic Arts, 

Durham, August, 1902. 



CONTENTS 



INTRODUCTION 

The Laboratory and its Equipment- 

The Cultivation and Preparation of Material 



CHAPTER 
I. 



BRANCH PROTOZOA: The One-celled Animals 
The Amoeba . 
The Euglena . 
The Paramecium 
The Vorticella 
The Stentor . 
The Stylonychia 
The Classification of the Protozoa 



II. BRANCH PORIFERA: The Sponges 
The Fresh-water Sponge 
The Marine Sponge .... 
The Classification of the Porifera . 



III. 



IV. 



BRANCH CCELENTERATA : The Hydras and Sea 

ANExMONES . 

The Fresh -water Hydra 

The Campanularian Hydroid 

The Hydro-medusa 

The Tubularian Hydroid 

The Classification of the Ccelenterata 



PAGE 

iii 
ix 
xi 

I 
I 
3 

5 

8 

9 
io 

12 

15 
15 
16 

18 



20 
20 

23 
26 
27 
29 



BRANCH TROCHELMINTHES : The Rotifers and 

their Allies 31 

The Rotifer, or Wheel Animalcule . . . 31 

The Classification of the Rotifers and their Allies . . ^ 



vi Contents 

CHAPTER PAGE 

V. BRANCH ECHINODERMATA: The Starfishes and 

Sea-urchins 35 

The Starfish 35 

The Sea-urchin 40 

The Sea-cucumber 42 

The Classification of the Echinodermata ... 44 

VI. BRANCH ANNULATA: The True Worms . . 46 
The Earthworm . . . . . . . .46 

The Marine Annelid 49 

The Classification of the Annulata .... 52 

VII. BRANCH ARTHROPODA: The Animals with 

Jointed Legs 53 

The Wood-louse, or Sow-bug ..... 53 

The Lobster, or Crayfish 54 

The Crab 60 

The Cyclops 62 

The Flattened Centipede ...... 64 

The Locust, or Grasshopper 65 

The Dragon-fly 68 

The Butterfly 71 

The Spider 72 

The Classification of the Arthropoda .... 74 

VIII. BRANCH MOLLUSCA: The Oyster, Clams, and 

Snails . 77 

The Clam 77 

The Snail 82 

The Squid 83 

The Classification of the Mollusca 85 

IX. BRANCH CHORDATA: The Vertebrates . . 87 

The Perch . 87 

The Frog 92 

The Bird 98 

The Classification of the Vertebrates . . . . 102 



INTRODUCTION 

THE LABORATORY: ITS EQUIPMENT AND THE 
PREPARATION OF MATERIAL 




_u^ 






Fig. i. A Movable Laboratory Table. 



vm 



INTRODUCTION 

THE LABORATORY AND ITS EQUIPMENT 

The zoological laboratory should be a well-lighted room, 
with sufficient space for each student to work comfortably. 
When possible it is better not to have direct sunshine 
through the windows during the hours of work. 

The laboratory must be fitted with some form of desks 
or tables, at which the student can work with ease. When 
good-sized laboratory tables were not available, I have 
found individual tables, like the one shown in Figure I, 
fairly satisfactory, especially for rooms which cannot be 
permanently fitted up with more expensive desks. Such 
tables have many advantages. On the one hand they are 
readily movable, so that the space can be divided accord- 
ing to the size of the class, no more desks being kept in 
the room than are needed for use ; they are made of differ- 
ent heights, so that they can be adapted to individual stu- 
dents ; they may be shifted about as the conditions" of the 
light may demand ; they enable the teacher to insist that 
each student shall work alone, without assistance from 
others ; and they prevent the joggling of the microscope of 
others when a pupil uses the eraser, or is restless at his 
desk. On the other hand, they are liable not to rest 
squarely upon the floor if it is not carefully laid, or has 
become worn through use, and in the form I have used 
there is no drawer in which to keep appliances. The 
addition of a drawer would render them more useful. 



x Introduction 

The desk illustrated in the figure is twenty-seven inches 
high, and is made of pine boards, one inch thick ; the top 
board is eighteen inches wide by thirty-two inches long. 

Whenever possible, each pupil should be provided with 
a compound microscope, magnifying to about five hundred 
diameters. There are, of course, many forms of micro- 
scopes to choose from. In selecting them, the aim must 
generally be to get the best instrument for the least money. 
In my own laboratory I have used with satisfaction the 
Leitz Stand No. 2, with objectives 3 and 7 and eye-pieces 
1 and 3, an outfit costing $17 when imported duty free. 
The stand has no rack and pinion adjustment, but it 
serves its purpose admirably. Similar simple forms of 
American makers will probably prove equally satisfactory, 
and there should be no difficulty in getting a microscope 
suitable for work in elementary zoology at the price named. 

If the pupils have not before used the compound micro- 
scope, a preliminary exercise should be given before the 
work in zoology is taken up. An excellent guide to such 
an exercise will be found in Dr. Charles H. Clark's " Prac- 
tical Methods in Microscopy," in which there are also given 
plain directions for preparing the few staining solutions 
called for in this manual. 

A few glass slides, cover glasses, and two or three watch 
glasses are necessary for each desk. A pair of small, 
sharp-pointed scissors, forceps, and scalpel are also needed, 
as well as a shallow tray or dish for the dissections that 
are to be done under water. Shallow pans of granite-ware, 
with sheet cork embedded on the bottom in plaster of Paris, 
serve very well ; but the wax-lined dissecting trays now on 
the market are the best of all. 

The teacher should be provided with the admirable 
" Text-book of Zoology," by Parker and Haswell, the 



Introduction xi 

classification of which is followed in this guide, and should 
have for reference as many other books on the subject as 
possible. Among the more important of these, mention 
may be made of the following : — 

Thomson's " Study of Animal Life." 
"The Riverside Natural History." 
"The Cambridge Natural History." 
Claus's " Text-book of Zoology." 
Lang's "Text-book of Comparative Anatomy." 
McMurrich's " Invertebrate Morphology." 
Packard's " Text-book of Entomology." 
Comstock's " Manual for the Study of Insects." 
Parker's " Elementary Biology." 
Hertwig's " General Principles of Zoology." 
Jordan and Kellogg's " Animal Life." 
Jordan and Heath's " Animal Forms." 

It is very desirable that some book should be studied 
by the class as a text-book to supplement the knowledge 
obtained through the laboratory study. 

THE CULTIVATION AND PREPARATION OF MATERIAL 

Perhaps the greatest difficulty that confronts the inexpe- 
rienced teacher of zoology is found in obtaining the mate- 
rial to be studied, in sufficient quantity and in good 
condition for class use. Success with the laboratory 
method of instruction in biological subjects renders it im- 
perative that the organism selected should be on hand in 
the right conditions and at the right time. To accomplish 
this, however, is no light task. The subjects are to be 
taken up in a certain definite order and at certain definite 
times, and the specimens studied, to be of the most value, 



xii Introduction 

must show the different phases of their growth. In those 
cases where the organisms are sufficiently abundant in the 
outer world to be available in quantity, it seldom happens 
that they present the desired phases of their existence at 
the time when it is necessary to study them. In a large 
proportion of cases they are not sufficiently abundant out 
of doors to be readily obtained in the needed quantity. 

Fortunately these difficulties may to a great extent be 
overcome by indoor culture of the organisms required. 
For several years I have been experimenting with such 
cultures, and in the following pages I have summarized 
such of the results as seem likely to be of assistance to 
those who use this book. The apparatus required for such 
cultures is simple and easily obtained. For the aquarium 
cultures, glass dishes and jars of almost any size and shape 
may be used. Perhaps no one general form is so cheap 
and satisfactory as the special aquarium jars recently 
placed upon the market by the dealers in microscopes and 
laboratory supplies. These are of convenient size and 
shape for cultures of many kinds, and a dozen or more of 
them are of the greatest value to the work of any zoologi- 
cal laboratory. Glass covers for them should be pur- 
chased. But in case these aquarium jars are not at hand, 
wide-mouthed museum jars or beakers, or even fruit cans 
and jelly glasses, will serve the purpose very well. 

THE AMCEBA 

Amoebae may be found in the waters of ponds and 
ditches, but one is more certain to have them when wanted 
by providing aquarium cultures. Almost any of the 
small aquaria described in these pages are likely to furnish 
good amoebae, if one examines the sediment that gathers 
on the sides or bottom of the vessel. I have often obtained 



Introduction 



Xlll 








THE AMCEBA: A, B, C, shapes assumed with pseudopods extended; B, shape 
when encysted ; £, shape when dividing. Magnified. 



xiv Introduction 

an abundance of fine specimens by placing small pieces 
of bark from trees or pond sides in small aquaria. After 
the culture vessel has stood in a warm room two or three 
weeks, remove the piece of bark from the water, and with 
a fine brush scrape off on to a glass slide some of the 
liquid adhering to it. Frequently there will be dozens of 
amoebae in a single mount. By floating a cover glass on 
the surface of the water of a jar containing amoebae and 
kept in a diffuse light for a day or two, specimens may 
be obtained free from sediment. 

In studying the amoeba, one should not be content with 
small amoeboid creatures having no contractile vacuole. 
The large typical specimens showing contractile vacuole 
and the nucleus may be obtained by a series of such 
aquarium cultures as are here described. If the aquarium 
is in a north window, it is well to put it in a warm sunny 
situation a few hours before studying, as the amoebae thus 
become much more active, and are of greater value for study. 
With such specimens the vacuole may be seen to contract, 
the distinction between the endosarc and the ectosarc may 
be made out, the ingestion and egestion of food particles 
may be observed, and my latest classes in zoology saw the 
whole process of reproduction by fission. 

The nucleus may be brought out in the amoeba by 
staining with iodine, methyl green, or blue, and with various 
other reagents. 

If the water in a culture jar in which amoebae are abun- 
dant is allowed slowly to evaporate, one will often be 
able to get good examples to illustrate the process of 
encystment. If the jar is finally allowed to become dry 
and is then stored away, the culture may be started again 
months later by adding water — a method first suggested, 
I believe, by Professor Herbert Osborn. 



Introduction 



xv 



THE EUGLENA 

I have generally been able to get the Euglena by this 
method : place pieces of bark an inch or more square, 
preferably from the edge of a pond, in the middle of a 
beaker or jar holding a pint or more 
of water. Set the culture vessel in a 
north window and let it stand. In a 
few weeks examine the upper and under 
surfaces of the pieces on the bottom, 
and you are likely to find Euglena 
viridis. 

Euglenae are also likely to be found 
on the sides and bottoms of many small 
aquaria. I have had fine lots of them 
develop in closed glass plant boxes, 
which had been temporarily used for 
keeping frogs. In small salt-water 
aquaria containing horse-shoe crabs 
they have also developed in great abun- 
dance- The Green Euglena: 

I have also obtained a fine lot Of Active form. Magni- 

Euglena viridis in this way : a glass 
dish two inches high by six inches in diameter was two- 
thirds filled with vegetable debris — largely pond, scum — 
from an old spring. It was then filled with water, covered, 
and placed near a window. After standing undisturbed 
nearly two months, a thick whitish scum had developed on 
top, and on the sides of the dish at the surface of the 
water there was a green growth composed almost entirely 
of euglenae. 

In summer and autumn the standing water in the 
' vicinity of barnyards is frequently full of euglenae in 




XVI 



Introduction 






THE Paramecium: A t normal active form; B, after treatment with acetic acid 
to bring out trichocyst threads ; C, conjugating specimens ; D t early stage of 
fission. Magnified. 



Introduction xvii 

excellent condition for study. Water from such a situa- 
tion may be placed in jars indoors, and allowed to stand 
some time with good results. 

THE PARAMECIUM 

Paramecia may commonly be developed by putting an 
excess of pond-scum or other water plants in a vessel 
containing water and setting the vessel in a warm, dark 
closet for a week. There will then probably be a whitish 
film on top of the jar; in this film you are likely to find 
an abundance of paramecia. Keep the jar in a warm, 
dark situation and they will continue to develop for some 
time. 

One of the finest lots of paramecia I have ever seen 
was developed in the following way : a cylindrical jar 
holding about two gallons (six inches wide by about fifteen 
inches high) was nearly filled with water and then was 
stocked with a mass of GEdogonium and other fresh-water 
algae, obtained from a spring, October 22. An excess 
of this was put in, and the jar was placed in a well-lighted 
room, six feet from a window. Five days later a rather 
thick film had formed on the top ; it contained an abun- 

: dance of large bacteria of various forms, a number of 
ciliate and flagellate protozoa, a few desmids and diatoms, 
as well as an occasional protococcus-like form. The sides 
of the jar showed bacteria, desmids, diatoms, Protococ- 
cus, Haematococcus, and a few euglenae. The bottom 
showed an abundance of the same forms. After this 
examination (October 27) I covered the jar and put it 
in a dark closet. On November 1 another examination 

J was made. The white film showed many ciliate infusoria, 
including some fine paramecia. Ten days later the water 

i 



xviii Introduction 

was alive with splendid examples of typical paramecia, 
white in color, which showed plainly the details of structure. 
Along the sides of the glass, just below the surface of the 
water, a white ring was visible to the naked eye, which 
under the lens was seen to be composed entirely of these 
paramecia, and the sides of the jar were also covered with 
colonies of Stentor polymorphns. In many cultures since 
then I have obtained these rings of paramecia. From 
such rings, hundreds of specimens may easily be transferred 
to the slide by means of a camel's-hair brush or a medicine 
dropper. 

Paramecia are also likely to be found in many small 
aquaria ; they are often abundant in those in which clams 
have been kept. But they can be studied to much better 
purpose when they are so abundant that one can have 
the large typical specimens in quantity. 

The course of the food-balls in the body may be admir- 
ably shown by this method : place a lot of paramecia in 
a watch glass with a small quantity of water ; add a little 
powdered carmine to the water ; cover, and examine fresh 
specimens at intervals of ten minutes for an hour or more. 
You will be able to trace the whole course of the food-balls 
in this way. 

The nucleus of Paramecium may be brought out by 
staining with iodine, magenta, methyl-green, or other stains. 
The trichocyst threads may be brought out by running 
under the cover glass a dilute solution of osmic, picric, or 
acetic acid. The form of the body is sometimes well 
shown when Schultze's solution is added. 

Paramecia should be first studied under the low powers 
with little or no cover-glass pressure. The normal shape 
can then be seen. The pressure of the cover glass flattens 
the body. By placing a little cotton-wool beneath the 



Introduction 



xix 



cover glass the movements of the paramecia may be 
restricted so that they are more easily studied. 




THE VORTICELLA 

Vorticellae occur in nature in ponds and sluggish streams, 
but are difficult to find in such situations in sufficient 
quantity for class use. 
They may be cultivated 
in aquaria without diffi- 
culty. They are likely 
to develop in shallow 
dishes containing 
aquatic plants of any 
kind, especially if the 
dish be placed in a dark 
situation. In the aqua- 
rium in which such a 
great quantity of para- 
mecia were developed, 
as described above, large 
numbers of vorticellae 
were also produced. 
Several cultures of vor- 
ticellae are desirable in 
order to get the divid- 
ing, the free-swimming, 
and the encysted stages. 
I have repeatedly ob- 
tained cultures showing 
each of these forms, the 
seeing of which adds much to the value of the study by 
the class. 





V A 

THE VORTICELLA : A, stalked form; B, free- 
swimming form; C, encysted form. Mag- 
nified. 



xx Introduction 

THE STENTOR AND STYLONYCHIA 

Stentors are generally harder to develop in indoor cul- 
tures than the common infusoria. But I have •usually- 
had them present in some one of the culture jars, frequentl) 
in those in which paramecia are found. Stylonychia is 
also generally present in Paramecium cultures. 

SPONGES 

Fresh-water sponges occur as bright green growths 
attached to stones and wood in shallow streams. The 
shade of the green is different from anything else in the 
environment, and together with the distinct spongy feeling 
of the organism will enable any one to recognize it. It 
frequently spreads over a considerable surface. 

These sponges are common in brooks, and may generally 
be found in abundance in the little pools between the 
large stones where the stream is rapid. They should 
be studied fresh, as they do not bear confinement in 
standing water very well. The gemmules occur late in 
autumn. 

The salt-water sponges are common along the coast, 
and may easily be gotten from pools when the tide is out. 
For inland schools they may be purchased of dealers in 
biological supplies. 

HYDRA 

This creature has a small cylindrical body, by the base 
of which it attaches itself to various objects in the water, 
and from the other end of which project a number of 
tentacles. Both the body and the tentacles are capable 
of being expanded and contracted, so that sometimes they 



Introduction 



xxi 



are long and slender, and at other times short and 
thick. Their appearance when slightly magnified is 
shown in the figure herewith. Two species are com- 
monly found : in one the body is green ; in the other it 
is light brown. 

Hydras are common in ponds and ditches, but are 
difficult to obtain in quantities under natural conditions. 
To collect them the following method is recommended : 



TxitT i t x t.o..yLUxrLaxLrtx 






The Hydra. Magnified. 



Bring in from various situations in ponds or sluggish 
streams small quantities of water-weeds, — as Nitella, 
Spirogyra, or Vaucheria, — collecting them with a small 
quantity of water in jars or cans, and labelling each so as 
to know where it came from. Place the material of each 
collection in a jar of clear water near a window, and let it 
stand for a day or two. Then examine the jar carefully, 
especially the sides near the window, for hydras. In this 
a reading glass is very helpful. In case hydras are found 



XX11 



Introduction 



in one jar, get more of the material from the same place 
and treat it in the same way. The hydras may be trans- 
ferred to covered aquaria containing Vaucheria, Nitella, or 
similar plants, where under favorable conditions they 
will multiply and be available when wanted. 

With a dozen or more aquaria containing water plants 

in good condition in the 
laboratory, hydras are 
pretty sure to be present 
in some of them. Water 
snails should not be al- 
lowed in hydra jars. Cy- 
clops or other minute 
Crustacea are also likely 
to be found in some of 
these jars. 

Marine Animals, — The 
various marine forms 
treated of in this book 
may be purchased in 
good condition for study, 
at small expense, from 
the Supply Department, 
Marine Biological Labora- 
tory, Woods Holl, Mass., 
as well as from various 
other dealers in such ma- 
terials. 




Cyclops. Magnified. 



INSECTS 



It is of course necessary that insects should be collected 
during the season when they are abundant. Some of them, 



Introduction xxiii 

like beetles, grasshoppers, and crickets, may be preserved in 
alcohol ; while others, like the butterflies, may be kept dry, 
although part of these may well be preserved in alcohol. 
To collect many of the insects a net is needed. To make 
it, obtain an iron wire about a fifth of an inch in diameter, 
bend it into a ring about a foot in diameter, with the ends 
projecting two or three inches at right angles; solder the 
ends into a short piece of brass tubing. Then sew over the 
wire a strip of strong muslin an inch or two wide, and to 
this muslin sew a bag of mosquito netting, Swiss muslin, 
or some similar fabric, about thirty inches deep. When 
in the field ready to collect, cut a handle for the net, or 
make one beforehand that will fit into the piece of brass 
tubing. 

The most convenient method of killing insects is by the 
use of the cyanide bottle. To make this, take almost any 
wide-mouthed glass bottle with a tight-fitting cork. Place 
on the bottom two or three lumps of cyanide of potassium 
(a virulent poison to be handled with great care), the size of 
a hickory nut, cover these with fine sawdust, and over the 
sawdust pour in sufficient plaster of Paris mixed with water 
to make a layer half an inch thick. Let the bottle dry out 
before inserting the cork. As already stated this cyanide 
of potassium is poisonous, and of course must be handled 
carefully. If desired, the bottles may be prepared at drug 
stores at small cost. After the plaster is set, there is prac- 
tically no danger unless the fumes of the bottle be directly 
inhaled, for which there is no excuse. Keep the bottle 
closed except when putting in an insect. The cyanide 
fumes rising through the porous plaster will kill it almost 
instantly. This cyanide bottle is to be used especially for 
butterflies and moths, as well as for bees, wasps, and similar 
insects, but should not be used for worms and caterpillars, 



xxiv Introduction 

which are more successfully killed and preserved in 
alcohol. 

Insects which have been kept dry for some time should 
be placed in a moist chamber (a tight jar with a little water 
or a damp sponge in it) for several hours to soften them 
before being used. 

Crayfishes for class use are easily obtained in many 
parts of the United States. In the Eastern States, where 
it is more difficult to get them, they may be bought of the 
following firms : Middleton, Carman & Co., Fulton Market, 
New York, N.Y., or Shattuck and Jones, Faneuil Hall 
Market, Boston, Mass. 

Live lobsters may also be bought of these or other 
merchants, but the crayfishes are less expensive and more 
convenient for study. — c. m. w. 



A LABORATORY GUIDE FOR BEGIN- 
NERS IN ZOOLOGY 



LABORATORY GUIDE UN ZOOLOGY 



CHAPTER I 
BRANCH PROTOZOA: THE ONE-CELLED ANIMALS 

THE AMCEBA 

It is very desirable that good-sized specimens be pro- 
vided for the study of the Amoeba. Under the high 
power of the microscope look for a small, granular, nearly- 
transparent object, which changes its outline either con- 
stantly or at frequent intervals. 

I. — Notice the general nature of the movements. Are 

they slow or fast ? Does the Amoeba always move in a 
definite direction ? Does it ever happen that different 
parts of the body move in different directions at the 
same time? Make five outline sketches showing the 
changes undergone by one Amoeba. 

II. — Study the method by which movement takes place. 
See that the outer colorless layer of protoplasm — the 
ectosarc — rolls out into one or more blunt projections, 
called pseudopodia, or false feet. See whether the inner, 
more granular protoplasm — the endosarc — is forced 
into the pseudopods by the lateral pressure of the 
ectosarc. Observe the changes in the outline of the 
body due to the movement of the pseudopods. In 



2 Laboratory Guide in Zoology 

case the Amoeba is moving in a definite direction, 
notice whether the progress is being made by means 
of a single broad pseudopod or by more than one. 
Determine whether a change in the direction of move- 
ment is made by pushing any part of the surface of 
the protoplasm outward. Is it true that the body of 
the animal is thus temporarily differentiated into an- 
terior and posterior parts ? 
III. — Watch the Amoeba as it approaches some small, 
one-celled plant. Wait patiently to see, if possible, the 
plant-cell taken into the body of the Amoeba. How is 
this accomplished ? Is any water taken into the body 
with the plant-cell ? 

IV. — Focus carefully upon a round, nearly transparent 
spot generally to be seen in the ectosarc : this is the 
contractile vacuole. Watch this spot patiently to see 
whether it ever disappears. If it does thus disappear, 
watch for its reappearance. 

V. — In the largest specimens look for the roundish 

nucleus, more granular than the endosarc surrounding 
it. If it is not visible in the living Amoeba, stain the 
specimen with iodine or carmine to bring it out. 

VI. — One is rarely fortunate enough to see the process 
of fission in the Amoeba, but sometimes this happens. 
If a large Amoeba is seen partially divided near the 
middle, watch it closely to see if division is taking 
place; if so, continue watching until the process is 
completed. 

VII. — Draw an Amoeba, making the sketch at least an 
inch in diameter: show its form, the distinction between 
the ectosarc and endosarc, the contractile vacuole, and 
the nucleus. 



Branch Protozoa 



THE EUGLENA 



The Euglena may be found in a resting or active condi- 
tion ; if resting, its form is generally almost or quite spheri- 
cal. In finding and studying it, use the high power of the 
microscope. 

I. — Study the free-swimming movements of the active 
organisms : do they always move straight ahead, or do 
they sometimes twist and turn about ? Watch the eugle- 
noid contortions of the body ; make five outline sketches 
showing the changes undergone by a single specimen. 
See whether the shape assumed when swimming freely 
straight ahead is generally the same in different indi- 
viduals. Distinguish between the anterior and poste- 
rior ends of the body. Watch the animal turn round 
and round on its longitudinal axis : does it show any 
differentiation into dorsal and ventral regions ? 
II. — The direct cause of locomotion will be found in the 
constant vibratory movement of a single hair-like pro- 
cess, about one-half as long as the body and projecting 
from the anterior end. It is to be seen most plainly in 
the largest specimens. This is the flagellum : it is a 
part of the protoplasm of the body, differentiated for 
the purpose of locomotion ; it is permanent in the active 
form of the Euglena, and cannot be withdrawn like 
the pseudopod of the Amoeba. By careful focussing, 
one can get glimpses of the cone-like cavity with the 
apex pointing inward, from the inner end of which 
the flagellum arises. This cavity serves the purpose 
of mouth and gullet, into which the vibration of the 
flagellum brings particles that serve as food. See 
the vortex in the water caused by the movement of 
the flagellum. 



4 Laboratory Guide in Zoology 

III. — Notice the green color of the Euglena due to chlo- 
rophyl — the green coloring-matter of plants. By 
means of this the creature is able to build up its sub- 
stance as plants do. Add a little alcohol, and notice 
what effect it has upon the color of the Euglena. 

IV. — After the alcohol has thus been added, notice the 
oblong bodies near the middle of the Euglena : these 
are paramylum grains. 

V. — In a freshly mounted specimen study the proto- 
plasm at each end of the body. How does its color 
differ from that of the central part of the body ? Near 
the front end see a distinct red spot, often called the 
eye-spot. Near this eye-spot distinguish the large clear 
reservoir with the vacuole beside it. The distinction 
between these may be plainly seen only in the largest 
and best specimens. 

VI. — Stain the specimens with iodine or carmine; then 
look for the nucleus, a round spot near the middle of the 
body. If it does not show clearly, take a fresh slide, 

. treat with alcohol to dissolve out the chlorophyll, and 
then stain. 

VII. — Make a drawing at least an inch long, showing an 
outline of a free-swimming Euglena and all the struc- 
tural details you have seen. 

VIII. — Study as many stages of the round Euglenas under- 
going fission as you can find. Make sketches of two or 
three specimens showing different phases of the process. 



Branch Protozoa 



THE PARAMECIUM, OR SLIPPER ANIMALCULE 

For a successful study of the Paramecium we must ob- 
serve the animal alive in water. Find it with the low 
power : it will appear as a slipper-shaped creature swim- 
ming rapidly about. To prevent its escape from the field 
of vision so that it may be studied with the high power, it 
is often desirable to put a few fibres of cotton under the 
cover glass. The same end may also be accomplished by 
drawing off much of the water on the slide by means of 
blotting-paper, but one should remember that the pressure 
of the cover glass may thus flatten the Paramecium. 

I. — Determine whether the animal moves in a definite 

direction without changing its outline. Does it move 
both backward and forward ? By focussing carefully, 
with light from the small opening of the diaphragm, 
determine the cause of movement. The short delicate 
hair-like processes around the margin of the body are 
called cilia. Do they vibrate when the animal moves ? 
Can you see any difference in the motion of the cilia 
when the animal is going forward and backward ? 

II. — Study the animal as it swims: does it revolve on 
its longitudinal axis ? Can you see a spiral groove on 
one side of the body ? It is called the buccal-groove. 
How long is this groove as compared with the body ? 

III. — Watch the Paramecium as it moves in and out 
among the particles on the slide. How does its flexi- 
bility compare with that of the Amoeba ? See whether 
the liquid endosarc flows back and forth within the body 
in response to the pressure of the ectosarc. 

I IV. — Determine whether locomotion is made with either 
end foremost. Is the blunter or the more pointed end 



6 Laboratory Guide in Zoology 

usually ahead ? In case either of these is generally 
in advance there is a differentiation into anterior and 
posterior parts of the body. 

V. — As the Paramecium turns on its longer axis, notice 

whether the edges of the buccal-groove are covered 
with cilia; are these longer than those on the rest of 
the body ? Are they constantly in motion ? Focus 
carefully to see the gullet connecting the buccal-groove 
with the interior of the body. Is this also lined with 
cilia in motion ? 

VI. — Run some powdered carmine under the cover glass : 
when the particles have reached the Paramecium, 
watch carefully to see some of them taken along the 
buccal-groove through the gullet and into the body. 
Notice that a little water goes in also, forming a 
small, round food-ball that stops near the inner end 
of the gullet, surrounded by the semi-liquid endosarc. 
When another food-ball is taken in, the first one will 
be forced along, keeping near the side of the body. 
When a third mass is taken in, both the others will be 
pushed along, and thus the process will continue, the 
masses following a definite course around the outer 
border of the endosarc. 

VII. — The course of the food-balls in the body may be 
easily shown in this way : Place a lot of Paramecia 
in a watch glass with a small quantity of water ; add 
a little powdered carmine to the water; cover, and 
examine fresh specimens at intervals of ten minutes 
for an hour or more. You will be able to trace the 
whole course of the food-balls by this method. 

VIII. — See the two round, nearly transparent contractile 
vacuoles near the side of body, each about halfway 
between the middle and the end. Watch them care- 



Branch Protozoa 7 

fully, to see the contraction : as the round spot dis- 
appears see the radiating canals surrounding it. Then 
see the expansion by which the vacuole resumes its 
former shape and size. 

IX. — The egestion of indigestible material may sometimes 
be seen by patient observation. Watch one or more 
particles that have completed the circuit which the 
food-balls follow, and have come to rest near the pos- 
terior end of the body. If you are fortunate, you will 
see a slight movement of the inner protoplasm, and the 
particles in question will suddenly be seen lying on the 
outside of the animal. As no opening in the body 
wall is visible, it is evident that the particles passed 
through a temporary opening. Since this usually takes 
place at the same spot, it is probable that the body wall 
is adapted at this point to the performance of this 
function. 

X. — Stain the Paramecium with iodine by putting a drop of 

the coloring-matter on the slide, and drawing it under 
the cover glass with blotting-paper. This will bring 
into view a large nucleus, generally near the gullet : 
and perhaps also the smaller micronucleus, lying beside 
the nucleus. 

|XI. — With a fresh mount, focus carefully along the side 
of the body to see the short, dark, oval trichocysts, per- 
pendicular to the surface. Run a little dilute acetic 
acid under the cover glass, and watch the long, hair- 
like processes — the trichocyst threads — thrown out 
from the surface of the body. 

XII. — Should you see one of the Paramecia with a con- 
striction on each side of the body at the middle, 
observe it closely: it is undergoing fission, the simplest 
method of reproduction employed by this species. 



8 Laboratory Guide in Zoology 

XIII. — Draw a Paramecium, showing the structure as 
you have observed it. Make the sketch at least two 
inches long. 

THE VORTICELLA, OR BELL ANIMALCULE 

The Vorticella is usually attached by one end to some 
stationary object. Its movements thus being confined to 
a narrow range, it is comparatively easy to study under 
high powers of the microscope. 

I. — Notice the two principal divisions — body and stalk. 

Compare the animal with a bell, and see at what part 
of the bell the stalk is attached : this part is called the 
proximal end. Tap the cover glass gently, and notice 
the sudden contraction of the stalk into a spiral and 
the change in the shape of the body. Watch the 
creature as the stalk straightens out and the body 
resumes its previous shape. 

II. — Focus carefully on the stalk to determine its structure. 
Can you see a slender band — the axial fibre — on the 
inside of the cylindrical outer portion ? 

III. — Study the outer or distal end of the body. Watch 
the ring of cilia immediately within the enlarged edge 
of the bell — called the peristome — within and partly 
attached to which is a flattened disk. Between the 
edge of the disk and the peristome on one side, is the 
mouth, which leads into the gullet. The latter is lined 
with cilia, and leads directly to the inner protoplasm 
of the body. Add a little powdered carmine to the 
slide, and see if you can observe the taking in of the 
food. 

IV. — A contractile vacuole may be seen in the body near 
the gullet. Watch its action. Distinguish also, if you 



Branch Protozoa g 

can, in the living Vorticella the long, curved, horseshoe- 
shaped nucleus. If it is not seen, stain the specimen 
to bring it out. 

V. — You are likely to find sometimes two Vorticellas upon 

the same stalk : this represents the last stage of fis- 
sion. Sometimes other stages of division will be found, 
and occasionally a free-swimming Vorticella may be 
seen, with a ring of cilia around the posterior margin. 

VI. — Make a good-sized drawing of a Vorticella, and 
sketches of any of the reproductive phases you may 
have found. 

THE STENTOR 

Although at times the Stentor is a free-swimming body, 
moving around as readily as the Paramecium, when 
found attached it may be studied as easily as the Vorticella, 
which it resembles somewhat in shape. It is one of the 
largest of the Infusoria, being easily visible to the naked eye. 

I. — Find the Stentor and study its movements with the 

low power. Note the various shapes that it assumes : 
sometimes it appears as a long, blunt, revolving cylin- 
der, swimming through the water ; at others, it stretches 
out and becomes pear-shaped, usually being attached 
at such times to some object by its smaller end. 

II. — When a Stentor thus becomes attached, study it care- 
fully. See the movements of expansion and contrac- 
tion. Observe the anterior disk, and the cilia encircling 
it. Add a little powdered carmine to the slide to 
demonstrate the manner of feeding ; see the particles 
pass down the spiral groove into the endoplasm, where 
they become a food-ball which is pushed farther into 
the protoplasm as time goes on. 



io Laboratory Guide in Zoology 

III. — Study the contractile vacuoles. How many can you 
find? ' 

IV. — Near the middle or front of the body find a mass 
of food material contained in a well-defined spherical 
cavity, somewhat larger than the contractile vacuole. 
This is called the excrement vacuole. Indigestible 
matter from all parts of the body is forced into this 
vacuole, whence it is extruded through the body wall. 
Egestion may, however, take place at other points. 

V. — By careful focussing, make out the longitudinal stria- 

tums of the Stentor. These are due to a differentiated 
portion of the ectosarc, by the contraction of which 
shortening of the body takes place. Determine whether 
there are cilia all over the surface of the body. 

VI. — See the remarkable chain-like nucleus along one side 
of the body. It can frequently be distinguished before 
staining, but if it is not visible in your specimen, add 
some staining solution to bring it out. 

VII. — Make a good-sized drawing of the Stentor, showing 
the parts visible when it is stretched out. Make also 
a sketch showing its shape when contracted. 

THE STYLONYCHIA 

In the first search for Stylonychia remember that it is 
shorter than the Paramecium, although it resembles the 
latter somewhat in general shape. 

I. — Observe the quick, jerking movement in its locomotion. 
By the use of a bit of blotting-paper, draw out some of 
the water on the slide, to restrain its movements so that 
it may be studied with the high power. Watch the ani- 
mal carefully to determine its anterior and posterior ends. 
Try to see if there is a rotary movement of the body. 
Determine whether it has a dorsal and a ventral side. 



Branch Protozoa 1 1 

II. — Watch the motion of the cilia on the surface of the 
body, and see the effect produced by such motion. If 
the Stylonychia forces itself along among the particles 
on the slide, notice the flexibility of the body. 

III. — Find two or three groups of spine-like processes much 
larger than the cilia. Are they movable ? See if you 
can determine their use. 

IV. — Find the gullet, appearing as a light streak near the 
centre of the body. Notice the motion within the gul- 
let. Trace the buccal-groove from the gullet to the end 
of the body. Observe the enlarged cilia along it. Ob- 
serve the relation between the buccal-groove and the 
direction in which the creature moves. 

V. — Run a little powdered carmine under the cover glass. 

Wait a little until it reaches the Stylonychia ; then see 
if you can observe the passage of some of the particles 
into the body. By patient watching, the course of the 
food masses through the body may be traced, the pro- 
cess being similar to that already seen in the Paramecium. 

VI. — The indigestible particles are forced out through the 
ectosarc near the posterior end. Find if you can a 
mass of particles to be egested ; observe intently the 
surface near the base of the spines, and quick, jerky 
twitchings of the protoplasm will be seen ; this forces 
out the particles. 

VII. — Observe the contractile vacuole and the two large 
nuclei ; to see the latter, it may be necessary to use a 
staining solution. 

VIII. — Draw a Stylonychia, showing the structural char- 
acters you have seen. Make the sketch at least an 
inch long. 



12 Laboratory Guide in Zoology 

THE CLASSIFICATION OF THE PROTOZOA 

The lowest branch of the animal kingdom is the Pro- 
tozoa. The members of this branch are nearly all aquatic, 
microscopic animals of very simple structure. They con- 
sist of a single cell, or in some cases of an association of 
cells, which are not, however, distinctly differentiated into 
tissues. The animals of this branch consist essentially of 
bits of protoplasm, each capable of absorbing food and 
reproducing its kind. Food is taken into the body; its 
digestible portions are assimilated, and its indigestible 
parts are rejected. The food so utilized may be either 
animal or vegetable in its nature. 

The Protozoa may be reproduced by fission, a process of 
simple division ; by budding, a process in which a small 
portion of the animal is divided off, separating from the 
parent cell, and finally developing into a new organism ; 
and by conjugation, a sexual process by which in certain 
forms two or more individuals fuse together, become en- 
cysted, and later split up into a large number of spores, 
each of which develops into an adult organism. There 
are various modifications of each of these processes. 

The Protozoa are now divided by leading authorities 
into five classes, namely : — 

I. Rhizopoda. 

II. Mycetozoa. 

III. Mastigophora. 

IV. Sporozoa. 
V. Infusoria. 

The members of the lowest class of Protozoa, the 
Rhizopoda, are usually characterized by the presence of 
an outer layer of protoplasm which frequently sends out 



Branch Protozoa 13 

temporary processes. The Amoeba is a typical example 
of this class, having a nucleus, nucleolus, and contractile 
vacuole. Under unfavorable conditions the Amoeba may 
become encysted and remain in that condition for a long 
time. Many Rhizopods are marine, secreting a covering 
or shell of carbonate of lime. The shells, falling to the 
ocean bottom when the animals die, in the course of geo- 
logic ages form vast areas of rock. Some of the most 
important animals carrying on this work are members of 
the order Foraminifera. 

The second class, Mycetozoa, consists of a group of 
organisms which are often included by botanists among 
plants, and called " slime-fungi." They so combine the 
characters of animals and plants that it is very difficult 
to say definitely to which kingdom they belong. They 
live upon decaying organic matter — such as leaves or 
damp wood, where they appear spread out in thin sheets 
of jelly-like protoplasm. 

The Euglena is a typical example of the third class, 
Mastigophora. The members of this group were formerly 
united with the Paramecium and similar animals to form 
the class Infusoria. Now, however, those creatures fur- 
nished with flagella are included in the Mastigophora. 

The fourth class, Sporozoa, consists of microscopic 
creatures living as parasites within other animals. The 
best known examples belong to the order Gregarinida, 
and live in the intestines of various insects and other 
Arthropods and worms. 

The members of the fifth class, the Infusoria, repre- 
sent the highest Protozoa. In these the protoplasm of 
the cell is generally differentiated on the outside into a 
somewhat hardened covering, inside of which is the more 
fluid protoplasm. All the members of this class are pro- 



14 Laboratory Guide in Zoology 

vided with short filamentous processes called cilia, which 
are outgrowths of the ectosarc. In some species, these cilia 
remain during the entire life of the animal, while in others 
they are present only in the young, being replaced in later 
life by peculiar organs called tentacles. The Paramecium, 
Vorticella, Stylonychia, etc., are examples of this class. 



r ■ 



CHAPTER II 
BRANCH PORIFERA: THE SPONGES 

THE FRESH-WATER SPONGE 

Upon the stones of clear running streams one can 
commonly see a greenish growth which at first sight is 
likely to be taken for an aquatic plant. If you rub 
your fingers upon it, however, you will notice a peculiar 
spongy feeling, and looking closely will find it very different 
from a plant. It is rather an example of the Fresh-water 
Sponge. Its more important features may be determined 
by means of the following outline : — 

I. — Study and describe the living sponge : its color, shape, 

size, surface appearance, and mode of attachment to 
the object on which it rests. In living specimens or 
those preserved in formalin, notice with a lens the 
minute openings in the surface, and see that there are 
two sets of holes, one larger than the other. Water 
containing food material enters the internal cavities 
through the smaller and goes out through the larger 
openings, the currents being produced by ciliated cells 
lining the passages. Observe also the tiny projecting 
spicules which form the skeleton of the sponge. 

II. — Feel the sponge with the tips of your fingers, noting 
the peculiar spongy texture. 

III. — Place a very small piece of the living sponge upon 
a glass slide ; tease it out with needle points, put on the 
cover glass, press it down firmly, and examine under 

15 



1 6 Laboratory Guide in Zoology 






the high power the margins of the sponge. You are 
likely first to see great numbers of very small, round, 
greenish cells ; these are a species of one-celled alga - 
a microscopic plant — which develops in connection with 
the sponge. Notice, also, certain much larger, spheri- 
cal, granular cells, having somewhat the appearance of 
a resting Amoeba. Imbedded in the protoplasm of 
these cells, there are likely to be many of the micro- 
scopic algae just mentioned. These larger cells are 
the ones that form the sponge " flesh." Some of them 
are likely to show movements similar to those of the 
Amoeba, and in consequence they are called amoeboid 
cells. Make drawings of one or more of them. 

IV. — Examine the margin of the particle of sponge : 
notice the soft cells connected with the whitish, needle- 
like spicules. 

V. — Place a small piece of sponge in caustic potash in a 

watch glass for an hour, then study the spicules under 
the microscope, after they have become separated from 
the tissues. Make drawings of three or four of them. 

VI. — Sponges collected during autumn and winter are 
likely to show peculiar yellowish spherical gemmules 
in the body. These are reproductive bodies by means 
of which the sponge passes through the winter. 






THE SIMPLE MARINE SPONGE 

(grantia sp.) 

This sponge is a marine animal, found commonly along 
the Atlantic coast of the United States. 

I. — Make a careful drawing of your specimen as seen 
through a hand lens of low power. Show in the 
drawing these parts : — 



Branch Porifera 17 

a. The general outline of the body, with its surface 
roughened by the presence of innumerable spicules. 

b. Beneath the rough surface of the spicules see the 
inhalent pores, scattered thickly over the wall of 
the sponge. 

c. The expansions at the basal end by which it is 
attached to the object upon which it grows. 

d. The terminal osculum, the opening at the upper or 
distal end surrounded by a funnel-like circlet of 
spicules. 

II. — Make with a sharp scalpel a longitudinal section of 
the sponge. Observe : — 

a. The central cavity into which the osculum opens; 
this cavity is called the cloaca. 

b. The many minute openings through the inside wall 
of the sponge are called the gastric ostia. 

c. In the cut surface of the sponge the numerous 
parallel canals, which connect the inhalent pores 
with the ostia. Make a diagrammatic drawing 
showing the structure of the sponge when thus 
seen in a longitudinal section. 

III. — Mount some of the spicules from the inside and out- 
side of the sponge and examine with compound micro- 
scope. Is there any difference in the appearance of 
those from the two situations? Draw specimens of each. 

This is an example of sponge life. The body is supported 
by the skeleton of spicules. Water containing microscopic 
plants or animals which serve as food is drawn through the 
inhalent pores into the parallel canals, where some of the 
food particles are taken up by certain cells. Then the water 
goes on through the ostia into the cloaca, and later passes 
out through the large osculum. 



i8 



Laboratory Guide in Zoology 



THE CLASSIFICATION OF THE PORIFERA 

The animal kingdom as a whole is broadly divided into 
two great groups, — the Protozoa, or one-celled animals, and 
the Metazoa, or many-celled animals. The examples 
treated of in Chapter I. all belong to the Protozoa, while 
the sponge is the first example of the Metazoa. 

The Porifera (formerly called sometimes Spongida) is 
the second phylum or branch of the animal kingdom, and 
the lowest of the Metazoa. 

For a long time in the early history of science the real 
nature of sponges was not understood. Naturalists could 
not agree as to whether they were plants or animals, or 
part plant and part animal. It has, however, been 
acknowledged for many years that they belong to the 
animal kingdom. After this point was reached there was 
much discussion as to their place in the kingdom. Some 
zoologists believed that they were simply masses of single- 
celled individuals living together, each for and by itself : 
consequently they placed the sponges in the Protozoa. It 
is now known, however, that a single sponge individual is 
made up of a great number of cells, all working for a com- 
mon end — the existence of the sponge individual. To do 
this well, some of the cells perform the function of protec- 
tion, some that of nutrition, while others serve the purpose 
of reproduction. In other words, the cells of the sponge 
organism are differentiated into tissues, those doing the 
same kind of work forming the same tissue. 

Sponges are aquatic animals of wide distribution : 
although most abundant in salt water, a few small chloro- 
phyl-bearing species live in fresh-water brooks and other 
streams. Their lives, except when they are very young, 
are spent attached to some submerged object where micro- 



Branch Porlfera 19 

scopic animal and plant life is abundant. Sponges as we 
ordinarily see them, either while living or after they have 
been treated for commercial purposes, convey to us no 
idea of the typical structure of the sponge. A bathing 
sponge, for instance, instead of being a sponge individual, 
is a colony of individuals formed by the budding and 
branching of an original sponge individual. The typical 

'sponge has but one large crater-like opening at its top, and 

' several smaller openings on its sides. Water currents 
enter the smaller openings, pass through the canals to an 

J interior cavity and escape through the large opening called 
the osculum. Food contained in the water is absorbed by 
the cells as it passes through the water-courses. The 

* outer covering of the body, the ectoderm, is a delicate 
membrane composed of a single layer of flat cells. A 

1 similar layer, the endoderm, lines the interior cavity and 
the canals leading to it. Between these is the mesoderm, 

' some of the cells of which have developed horny fibres, or 

' siliceous or calcareous spicules, which serve the purpose of 
a skeleton that is seen in commercial sponges, the living 

1 cells having been rotted and washed away. 



CHAPTER III 

BRANCH CCELENTERATA : THE HYDRAS AND THE SEA- 
ANEMONES 

THE FRESH-WATER HYDRA 

Either the green or the brown Hydra may be used for 
this study. Before the specimen is placed upon the slide 
beneath the microscope it is desirable that the student 
examine the specimens in the culture vessel. Notice their 
color, general shape, and mode of attachment. With a 
camel's-hair brush or small glass tube, remove the Hydra 
to a watch glass or a glass slide with a hollow cell, holding 
a little water, and study it with the low power of the 
microscope. 

I. — Observe the general form of the Hydra, noticing the 
shape of the body and of the projections, called tentacles, 
at its upper end. See that the most noticeable move- 
ments are the gentle lashings of these tentacles. 

II. — Study and describe the contraction and expansion of 
the body and of the tentacles. These movements are 
caused by the contractile power of muscle processes 
attached to the inner ends of those cells which form 
the outer layer of the body wall. 

III. — Sometimes the Hydra moves from place to place by 
bending the body into a loop and using each end as a 
foot. This is not usually to be seen, however. 

IV. — Watch again the slow sweeping movements of the 
tentacles. Possibly you may see one tentacle lay hold 
upon a small water-flea or other particle of food. If so, 



Branch Coelenterata 21 

it is likely to pass the food to the base of the tentacle, 
where, in the middle of a round projection, the mouth, 
opening into the body cavity, may be seen. 
V. — Make another careful study of the Hydra, endeavoring 
to see the hollow nature of its body and tentacles. This 
may sometimes be done by strong light when the 
animal is extended. Is the body cavity continued into 
the tentacles ? Encircled by the bases of the ten- 
tacles, see a cone-shaped extension of the body, the 
hypostome. How is the mouth situated with reference 
to the hypostome ? Unless you are fortunate in retain- 
ing the specimen in the right position, it will require 
careful manipulation with needles or other instruments 
in order to see clearly the mouth opening. 

' VI. — See that the walls of the Hydra's body and tentacles 
are made up of two layers of cells: the inner layer is 
called the endoderm, and the outer layer, the ectoderm. 
The colored appearance of the green Hydra is due 
to the pigmented chlorophyl. Focus carefully with 
strong light along the edge of the body or tentacles, to 
determine whether this chlorophyl is contained within 
the ectoderm or the endoderm. Make a drawing to 
show the double or diploblastic nature of the body wall. 

I VII. — Notice that the mouth furnishes the only entrance 
to the body cavity, which serves as a stomach. Food 
is pushed in by the tentacles through the mouth, and 
through it the indigestible matter is ejected by the 
contraction of the body. Note the fact that the food 
comes in contact with the endodermal cells only. 
These cells alone perform the function of digestion, and 
thereby exhibit a true division of labor among the cells 
of the organism. The ectodermal cells obtain their 
food only after it has been digested and passed through 



22 Laboratory Guide in Zoology 

the endoderm. True excretion, or the removal of waste 
material produced by chemical changes within the cells, 
is performed by the general surface of the body. 

VIII. — In the ectoderm of the tentacles try to find small, 
well-defined oval bodies near the margin. They are 
called nematocysts, are contained within nettle cells, 
and correspond in function to the trichocysts of the 
Paramecium. Within this oval sac there is a long, 
spirally coiled thread which the Hydra has the power of 
throwing out to wound its prey. Doubtless some poison 
ejected with the thread produces the wound. These 
organs are put to great use in capturing food, though 
none can be used a second time. You may see the 
threads by drawing acetic acid under the cover glass. 

IX. — Observe the Hydras in the culture jar once more. 
Try to find one that has a blunt projection on the side 
of its body or one that has a small Hydra attached to it. 
These are doubtless stages in the process of reproduction 
by the asexual method. There is also another way in 
which Hydras reproduce their kind — the sexual method. 
These processes are explained in the following sections. 

X. — Asexual Reproduction. Multiplication by this pro- 
cess is called budding. A blunt process or bud appears 
on the Hydra's side, formed at first only of ectodermal 
cells. This is gradually pushed out and filled with endo- 
dermal cells. As the bud increases in size, a cavity, 
continuous with that of the main body cavity of the 
parent Hydra, is developed within the mass of endo- 
derm. Later a mouth and tentacles are formed at the 
outer end of the bud ; its stalk is then constricted at its 
union with the parent, and the free-swimming young 
Hydra moves away. Some stages of this process of 
budding may be easily found by examining all the 
specimens at hand. 



Branch Coelenterata 23 

XI. — Sexual Reproduction. Light-colored blunt processes 
formed only of ectodermal cells appear on the body- 
near the tentacles. Such structures are the male 
reproductive bodies and are called spermaries. Their 
inner cells change into sperms, and when the thin wall 
holding them bursts, they go forth as free-swimming, 
pointed masses of protoplasm. 

XII. — Elevations similar to the spermaries also occur near 
j the basal end of the body. These are the ovaries, and 

are at first similar in structure to the spermaries. Their 
inner cells soqn disappear, with the exception of one 
large amoeboid cell, called the ovum. This soon be- 
comes freed from the Hydra, and is penetrated by a 
single sperm from some other Hydra. The process is 
called fertilization, and the fertilized ovum sinks to a 
sheltered place and soon develops into a Hydra. 

You will probably be unable to study this process by 
actual observation, since it is much more hidden and 
complex than that of budding. Any slight swellings 
on the side of the Hydras should, however, be care- 
fully studied, although it may be hard to distinguish 
between ovaries, spermaries, and young buds. 

THE CAMPANULARIAN HYDROID 
HYDRIFORM STAGE 

This little animal lives in colonies in shallow water along 
the seashore. 

I. — Examine through a hand lens or with the low power 
the specimen in your watch glass. Notice its general 
appearance. Is it attached to anything? Is there 
any variation in the color ? Observe the size of your 
specimen. 



24 Laboratory Guide in Zoology 

II. — Mount the specimen on a glass slide and observe it 
through the low power. Notice that the animal is 
composed of two general parts ; namely : — 

a. A firm outer covering, called the perisarc. 

b. An inner protoplasmic part — the living substance. 

III. — Identify the following five general divisions of the 
perisarc : — 

a. The root-like expansion, called the hydrorhiza, by 
which the stem is attached to whatever object it 
grows upon. 

b. The upright stem portion, forming the linear cylin- 
drical part of the colony. This is the hydrocaulus. 

c. The branches that have an open, conical, bell-like 

projection on the outer ends, inside of which are 
small hydra-like bodies with numerous tentacles : 
the projecting parts of the perisarc are called hydro- 
thecae, and the hydra-like bodies are called zooids or 
hydranths. 

d. Branches like those just described, but closed at the 
outer ends and having protoplasm inside : these are 
young hydranths in process of development. 

e. Branches that have a club-shaped tip, the gonan- 
gium, inside of which are small, rounded bodies, the 
medusa-buds. 

Make a drawing showing each of these parts and 
label them distinctly. 

IV. — Study the structure of the perisarc. Notice its thick- 
ness. Is it perfectly cylindrical throughout its length ? 
If not, where are the variations ? 

V. — Make a careful drawing of a single zooid or hydranth 

with the tentacles extended. Show these points : — 
a. The relation of the hydranth to the bell-like projec- 
tion of the perisarc, which is called the hydrotheca. 



Branch Coelenterata 25 

b. The connection of the base of the hydranth to the 
protop asm in the stem of the perisarc. 

c. The shi-pe of the body, including its basal part, its 
central part, the tentacles, the proboscis or manu- 
brium upon the tip of which is the mouth. 

VI. — Compare this hydranth with a Hydra. In what re- 
spects does it resemble the Hydra ? In what respects 
does it differ from it ? 

VII. — Study the tentacles carefully, using as high power 
as necessary. How many are there ? Is the number 
always the same on different hydranths ? How does 
their length compare with the length of the body of 
the hydranth ? See the little nettle cells. How are 
these arranged ? 
: VIII. — Study the different stages of the young hydranths. 
Make drawings of two or three of these stages. Are 
these young hydranths able to get food for themselves? 
If not, where does the material for their growth come 
from ? 

IX. — Trace the connection between a hydranth and the 
one next above it and next below it on the stem. Is 
the protoplasm continuous ? Can you find any in 
which a fully developed hydranth with tentacles is next 
to a partially developed hydranth ? 

X. — Make a careful drawing of a gonangium, showing the 
club-shaped perisarc portion and the round or oval 
bodies inside, as well as the protoplasmic connection 
with the main stem. The bodies inside are medusa- 
buds. In due time they escape from the club-shaped 
perisarc into the sea, where thev develop into small, 
free-swimming jelly-fishes, very different from the hy- 
droid colony. There are thus two sorts of generations 
of this animal — the fixed colony you have been study- 



26 Laboratory Guide in Zoology 

ing, and the free-swimming jelly-fish form. For this 
reason the species is said to have an alternation of 
generations. 

XL — In what part of the gonangium are the medusa-buds 
largest ? 

XII. — Are there any tentacles in connection with the 
gonangium, or is there any way in which it can get food 
from outside ? If not, where does the substance of 
which the medusa-buds are built up come from ? 

MEDUSOID STAGE OF A CAMPANULARIAN HYDR0ID 

I. — In your study of the hydriform stage of the Campanu- 

larian Hydroid you observed, 4n the gonangia, small 
bodies called medusa-buds. If you saw well-developed 
medusa-buds, you found them to be bell-shaped. When 
mature, these buds break away and escape through the 
opening in the distal end of the gonangium into the 
water, where they become at once independent, free- 
swimming animals. 

II. — Compare this free-swimming Medusa to an umbrella 
with the handle broken off short. The short handle is 
the manubrium. In its end there is an opening, which 
is the mouth. From the base of the manubrium to the 
margin of the circle run four ribs of the umbrella : 
these are radial canals. They open into a circular canal. 
Stretching horizontally from the circular canal toward 
the middle is a thin white membrane : this is the velum. 
The convex side of the umbrella is called the exumbrella 
or aboral surface, and the concave side is the subumbrella 
or oral surface. 

III. — Projecting downward from the outer margin of the 
umbrella are many rather long threads : these are the 
tentacles. About how many of them are there ? 



Branch Coelenterata 27 

IV. — Mount one of these tentacles on a glass slide, and 
observe its , structure with the low power. How are 
the nettle cells arranged along the tentacles ? Is there 
any difference in their arrangement near the basal end 
of the tentacle and near its distal end ? Make a care- 
ful drawing of a section from the basal part and of 
one from the distal part, including in the latter the end 
of the tentacle. 

V. — Now examine the tentacles with the high power. 

Notice the structure of the nettle cells. Make a draw- 
ing showing a bit of the edge of the tentacle with these 
cells imbedded in it. 

VI. — See the wart-like projections along the sides of the 
radial canals : these are the sexual reproductive organs. 
In some specimens these produce spermatozoa ; in others 
they produce eggs. The sexes are therefore distinct. 
The eggs are fertilized by the spermatozoa which have 
come from other medusae. Then each develops into a 
Campanularian Hydroid. 

VII. — Make a careful diagrammatic sketch of a side view 
of the Medusa, labelling the parts distinctly. 

THE TUBULARIAN HYDROID 

HYDRIFORM STAGE 

This is an animal living in salt water in rather good- 
sized colonies. It resembles in many respects the Cam- 
panularian Hydroid. 

I. — Examine the' specimen in your watch glass through 
a hand lens. Is the branching different from that of 
the Campanularian Hydroid ? Does the colony seem 
larger ? 



28 Laboratory Guide in Zoology 

II. — Mount a small part of the specimen on a glass slide, 
and observe it through the low power. Notice that 
like the Campanularian Hydroid it is composed of two 
general parts, viz. : — 

a. A firm outer covering, the perisarc. 

b. An inner protoplasmic part — the living substance. 

III. — Spread the colony out upon a flat surface and make 
a sketch of the whole of it. Identify the following 
divisions of the colony, and label them in your drawing : 

a. The root-like expansion — hydrorhiza — by which 
the colony is attached to the permanent support. 

b. The upright branching stem, the hydrocaulus. 

c. The terminations of the branches of the hydrocaulus, 

without the bell-like expansion of the perisarc which 
is present in the Campanularian Hydroid. 

d. The projecting zooids or hydranths on the ends of 
the terminal branches. 

IV. — Examine with the low power an individual zooid. 
Make a good-sized drawing in which you show clearly 
the following parts, labelling them carefully: — 

a. The basal connection with the perisarc. 

b. The ring of long tentacles near the base of the 
zooid. 

c. The ring of short tentacles toward the distal end. 

d. The projecting " proboscis" or manubrium on the 
distal side of the short tentacles. 

e. The mouth upon the tip of the manubrium. 

V. — Study several other hydranths to see what variations 

exist. Are there always the same number of long 
tentacles ? of short ones ? 

VI. — Study the tentacles under a higher power. Are there 
nettle cells present ? 

VII. — Compare this hydranth with the hydranth of the 






Branch Coelenterata 29 



Campanularian. In what respects are the two alike? 
In what respects are they different ? 
VIII. — Find two or three hydranths with medusa-buds 
growing upon the body wall. Make drawings of these, 
showing different stages of the development. 

THE CLASSIFICATION OF THE CCELENTERATA 

The third phylum or branch of the animal kingdom, and 
the second phylum of the Metazoa, is the Coelenterata. 
This phylum is characterized by individuals having a dis- 
tinct body cavity with but one external opening, the mouth, 
and a body w r all composed of two layers of cells, the ectoderm 
and the endoderm. Sometimes a thin or thick layer called 
the mesogloea occurs between the other two. The mouth 
corresponds to the mouth of higher animals, and the 
body cavity into which the mouth opens corresponds to 
the alimentary canal of the higher animals. The endoderm 
of the Coelenterata is homologous in general with the lining 
of the alimentary canal, and the ectoderm is homologous 
with the skin of the higher animals. 

The Coelenterata are universally aquatic animals, occur- 
ring most abundantly in salt water. There is generally a 
row of tentacles around the mouth, the cavities of these 
tentacles being continuous with the main body cavity ; they 
aid in the capture of food and in locomotion. Another 
characteristic feature of the branch is the possession of 
nettle cells, within each of which is a minute sac containing 
a fluid and a barbed filament capable of being thrown out 
for stinging purposes. They reproduce by budding, by 
fission, and by eggs. 

The Coelenterata are divided into four classes, of which 
the Hydrozoa and the Actinozoa are the most important. 
The members of the first class, the Hydrozoa, are the most 



3<d Laboratory Guide in Zoology 

typical and easily understood. Their structure is well 
illustrated by the common Fresh-water Hydra. Members 
of this class reproduce by budding, sometimes by fission, 
and sometimes by eggs. Many marine jelly-fishes belong 
to this class, although a majority of the large jelly-fishes 
are included in the second class, the Scyphozoa, and a few 
peculiar forms known as Comb-jellies are included in the 
Ctenophora, which forms the fourth and highest class of 
the Coelenterata. 

The members of the third class, called the Actinozoa, 
greatly resemble, and were long thought to be, marine 
plants. Here belong the sea-anemones and other soft- 
bodied polyps. The coral polyps, which secrete a kind 
of calcareous framework, also belong to this class. These 
animals, living a fixed life, constantly reproducing by fis- 
sion, have been the chief agency in building up our vast 
coral reefs and islands. 



CHAPTER IV 

BRANCH TROCHELMINTHES : THE ROTIFER AND ITS 

ALLIES 

THE ROTIFER, OR WHEEL-ANIMALCULE 

Find the specimen with the low power : some are likely 
to be moving about the field too rapidly to be studied; 
others may be temporarily fixed at the base, and simply 
moving within an area represented by the length of the 
body. These are the ones to study. If none such are 
found, extract the surplus water from beneath the cover 
glass with a piece of blotting-paper, to quiet some of the 
active Rotifers. In the study use both the high and low 
powers of the microscope. 

I. — Can you see two different ways of locomotion — one a 

crawling movement, the other a free-swimming move- 
ment? Describe each. Do the Rotifers always go 
forward when moving ? How does the locomotion of 
the Rotifer compare with that of the Amoeba ? Is there 
a distinct differentiation into anterior and posterior 
parts ? Is the movement in a definite direction ? 

II. — What decided difference can you see between the gen- 
eral structure of this creature and the other microscopic 
animals (like Paramecium, Stentor, or Stylonychia) you 
have studied ? Is the Rotifer a one-celled animal ? 

III. — Study and describe the tail-like structure on the pos- 
terior end of the body. Does it move from side to side, 
or disappear within the body, or both ? 

31 



32 Laboratory Guide in Zoology 

IV. — Learn whether the Rotifer revolves frequently on its 
longitudinal axis. Do you conclude that the animal 
has a dorsal and a ventral surface ? 

V. — The cause of the free-swimming movement will be 

easily made out. Notice that the head appears as if a 
revolving wheel were attached to its surface : in many 
species there are two disks showing this motion. This 
appearance is caused by the rhythmical motion of one 
or two bands of cilia encircling the disks of the head. 
These revolving cilia form one means of locomotion. 
Notice how the contraction of the body affects its 
movement. 

VI. — Study the hard, vase-shaped case into which the 
extremities of the body are drawn. Observe the 
degree of its flexibility as the Rotifer moves about. 
This case is called the lorica; in it are crowded the 
organs for ingesting, masticating, digesting, and assimi- 
lating food, and for egesting waste material ; also the 
organs of reproduction. 

VII. — Watch again the head and foot as they are drawn 
in, and notice that it is then much more difficult to 
distinguish the parts inside. Observe the Rotifer as it 
stretches out ; you will be able to see narrow bands 
passing along the body beneath the lorica. Similar 
bands encircle the body. These two sets form the 
muscular system of the Rotifer : the movements of the 
body are due to the contractile power of the muscles. 

VIII. — Add a few grains of powdered carmine to the water 
on the slide. When the particles come near an active 
Rotifer, see the vortex caused by the movements of the 
cilia. Watch for the swallowing of some of these 
grains when the head is suddenly drawn into the body. 
When two disks of cilia appear, the mouth may be seen 



Branch Trochelminthes 33 

between them. Distinguish if you can the gullet leading 
from the mouth, and lined with cilia. The so-called 
teeth are visible at the inner end of the gullet ; behind 
the teeth lie the stomach and intestine ; the latter ends 
in an opening on the under side of the lorica near its 
posterior border. 
IX. — Make a good-sized drawing of the Rotifer. 



THE CLASSIFICATION OF THE ROTIFERS AND THEIR ALLIES 

Early in the history of zoological science the Rotifers 
were classified with the Infusoria. But as soon as it was 
seen that they were multicellular animals, it was necessary 
to remove them from the branch Protozoa and to find for 
them another resting-place in the system of classification. 
No place seemed more fitting than the branch Vermes, 
which was formerly made to include the worms and various 
related creatures. It has long been recognized, however, 
that the Vermes was too heterogeneous a collection to sat- 
isfy the requirements of our knowledge, so that the latest 
authorities have divided it into several groups, each with 
the rank of a branch or phylum. The Rotifers, and two 
other less abundant classes of minute animals somewhat 
resembling the Rotifers, have been united to form the phy- 
lum Trochelminthes. The young of these creatures exist 
in the form of a trochosphere, which becomes modified dur- 
ing the development of the animal. The class Rotifera is 
much the most important one in this phylum. 

Four other groups have been separated from the Vermes 
and raised to the rank of independent phyla. One of these, 
the Annulata, is considerably higher than the rest and is 
discussed later in this book in connection with the earth- 
worm. 



34 Laboratory Guide in Zoology 

The lowest of these branches into which the old group 
Vermes has been broken up, is the branch Platyhelmin- 
thes, which includes the so-called Flatworms. These are 
soft-bodied, bilaterally symmetrical animals in which the 
body is generally compressed above and below so as to 
give a flattened appearance. There is not a distinct body 
cavity. This group includes many species, some of which 
live free in water of ponds and streams, while others are 
parasites; the tapeworm of man is an example of the 
latter. 

The next higher branch is called the Nemathelminthes, 
and includes the so-called Roundworms or Threadworms, 
the " Hook-headed worms/' and the " Arrow-worms." In 
general the body is cylindrical. The most important class 
is the Nematoda, which includes the " vinegar eels " and 
various small worms that live as parasites in the roots of 
plants, as well as the Trichina spiralis found in pork and 
often causing disease in man. 

The third group which has been separated from the 
Vermes is the Trochelminthes already discussed, while 
the fourth is the Molluscoida. This is composed of three 
classes ; namely : — 

I. Polyzoa. The " Sea-Mats " and " Corallines." 
II. Phoronida. Phoronis, a worm-like animal living in 

the sea. 
III. Brachiopoda. The Lamp-shells. 



CHAPTER' V 

BRANCH ECHINODERMATA : THE STARFISHES AND SEA- 
URCHINS 

THE STARFISH 

Starfishes furnish excellent objects for study, whether 
freshly killed or preserved in alcohol or formalin. The 
internal structure is best made out by dissecting under 
water. Of course the larger the specimens are the more 
satisfactory will be the results. Dried specimens are 
desirable for the study of the outer surface. 

EXTERNAL ANATOMY 

I. — What gives the animal its star-like appearance ? Dis- 

tinguish the flat ventral surface from the more rounded 
dorsal surface. To understand that the body is pentag- 
onal-shaped, imagine the rays cut off at their bases. 

II. — Compare the animal's symmetry with that of the frog. 
Notice the apparent absence of anterior and posterior 
ends. Such an arrangement may be called radial sym- 
metry. The following method, however, will enable 
you to understand that the arrangement of parts ap- 
proaches a bilateral symmetry, or such an arrangement 
of parts that the whole may be divided into two similar 
halves : Find a smooth circular white, yellow, or orange 
spot — the madreporite — near one side of the dorsal 
disk and near the angle formed by two adjacent rays. 
Will an imaginary line drawn from the madreporite 
across the starfish divide it into two similar parts ? 

35 



36 Laboratory Guide in Zoology 

III. — With a pocket lens observe quite carefully the ap- 
pearance of the rough dorsal and lateral surfaces. Find 
as many kinds of projections as you can. The hard- 
pointed projections, or spines, are developments of the 
body wall, and are used for purposes of protection. 
Around the bases of the spines are the forceps-like 
pedicellariae. 

IV. — The soft blunt projections afe hollow processes of the 
body wall. They allow the fluid of the body cavity — 
visceral fluid — to come into contact with the external 
water and air, and are called papulae or respiratory coeca. 

V. — Find a small anal opening, lying near the centre of the 

dorsal disk on a line drawn from the centre of the 
disk to the angle formed by two rays. 

VI. — Place the animal upon its back, and observe its ven- 
tral surface. Notice the five grooves, one in each ray, 
terminating internally at the side of a pentagonal- 
shaped depression. Because these grooves contain 
organs of locomotion they are called ambulacral 
grooves. 

VII. — Notice that beneath this pentagonal-shaped depres- 
sion a colorless membrane with a small opening in its 
centre is stretched. This is the peristome, and the 
opening in the peristome is the mouth. The peristome 
is connected with the wall of the alimentary canal. 

VIII. — Observe the kind of organs that fill the ambulacral 
groove. They are short, cylindrical structures called 
ambulacra or tube feet. How many rows in each groove ? 
The tube feet are a part of quite a complicated system 
which serves the function of locomotion and possibly 
of respiration. 

IX. — With the forceps, push aside the two inner rows of 
tube feet, so that you can look down into the very roof 



Branch Echinodermata 37 

of the groove, See if you can find there a small, 
white thread-like structure — a nerve trunk — sending 
out branches to the feet. Follow this to the end of the 
ray, where it ends in the midst of a little bunch of 
spines. Look at this bunch of spines carefully with a 
pocket lens. Examine the termination of each ray in 
this way. Is there any connection of the nerve trunk 
with the red spot at the end of the arm ? This spot is 
sensitive to light, and for that reason is called the eye- 
spot. Follow the nerve trunk to its inner termination 
at the base of the ray Is it connected with the circu- 
lar nerve ring, surrounding the peristome and the 
mouth ? 

INTERNAL ANATOMY 

X. — With sharp-pointed scissors, remove the integument 
from the dorsal surface of one of the rays, being very 
careful not to disturb any of the underlying parts. 

Remove also the body wall from the main dorsal sur- 
face, leaving the madreporite untouched. Be espe- 
cially careful to harm none of the internal organs when 
removing this part of the body wall. 

XI. — Observe the following structure : Two long pointed, 
brown, lobulated bodies lie side by side, nearly filling 
the ray from base to tip. These are digestive glands 
(that is, organs the cells of which secrete a digestive 
fluid) ; they are called hepatic coeca. 

XII. — Notice the colorless ducts running along the centre 
of these masses, uniting near the bases of the ray. 
Follow up this common duct, and see that it empties 
into a flat, membranous, pentagonal-shaped sac, a part 
of the stomach called the pyloric sac. Below this is 
the stomach proper, with which the pyloric sac is con- 
tinuous. 



3^ 



Laboratory Guide in Zoology 



XIII. — Above the pyloric sac is the intestine, but on ac- 
count of its small size it was probably torn away with 
the body wall. Make out a similar connection between 
the pyloric sac and the digestive glands in the other 
rays. 

XIV. — Upon the surface now exposed, muscles were ar- 
ranged which lifted the rays and moved them from 
side to side. They were probably cut away when the 
integument was removed. Try to find parts of them 
extending from the centre of the body along the me- 
dian line of each ray. 

XV. — Turn back both hepatic coeca and observe the 
stomach carefully. Notice its large, blunt projection, 
the cardiac pouch, extending into each ray a short dis- 
tance. Push this carefully aside, and see the narrower 
part below, corresponding to an oesophagus or gullet, 
into which the mouth opens. 

XVI. — On each side of the ray, at its very base, and 
attached to the walls separating that ray from the adja- 
cent rays, find two small white or orange colored lobed 
bodies, shaped something like a single digestive gland : 
these are the reproductive bodies. At the place of 
attachment, there is an opening in the body wall for the 
passage of the contents. See if there are two, similarly 
placed, in each of the other rays. These organs are 
either ovaries or testes ; that is, the sexes are separate. 
The eggs are fertilized, and the development of the 
young starfish takes place outside of the body. 

XVII. — You will notice a very interesting arrangement of 
the parts now exposed on the floor of the ray. Keep 
the specimen constantly under water. See four rows 
of colorless, inflated, closed tubes : they resemble in 
arrangement the tube feet just below them on the 



Branch Echinodermata 



39 



under side of the ray. These structures are called 
ampullae (a single one is called an ampulla), and are 
directly connected with the tube feet. In fact, an 
ampulla is an enlarged extension of a tube foot. At 
the junction of the ampulla and the tube foot, there is 
a short tube connecting them with a long one which 
passes close to the nerve trunk along the roof of the 
ambulacral groove. 

This long tube passes the entire length of the ray, 
and connects with a pentagonal, or rather circular, tube 
around the peristome. Carefully push aside the parts 
lying beneath the madreporite, and you will see a long, 
hard, white tube extending downward. This is called 
the stone canal. Does it connect with the circular 
tube just mentioned? The madreporite is very finely 
perforated, and through these openings water passes 
down the stone canal, filling the circular tube. From 
the circular tube the water passes along the radial 
tubes in the arms, and from them into the short branch 
tubes leading to the ampullae and tube feet. The 
whole system is called the water-vascular system. A 
patient study is required to understand well the ar- 
rangements of parts in this system. 
XVIII. — Learn how locomotion is performed by the water- 
vascular system. As has been said, the system is filled 
with water through the pores of the madreporite. 
Water is forced from the ampullae into the tube feet, 
throwing them forward. The contracting walls of the 
tube feet then force the water back into the ampullae, 
and suction makes the feet stick to the surface upon 
which they were lying. The body may be then drawn 
forward and the operation of extending the feet re- 
peated. From what you know of the animal's mode 



4<d Laboratory Guide in Zoology 

of locomotion, would you say that it possesses anterior 
and posterior parts ? 

XIX. — The blood system you will probably be unable to 
make out. It has the same general arrangement as 
the nervous and water systems, that is, a circular ring 
around the peristome, which sends out five branches of 
vessels, one to each ray. 

XX. — Dissect each of the remaining rays, varying the 
operation to suit the necessity of clearing up any 
points not at first understood. Make drawings. 

THE SEA-URCHIN 

The Sea-urchin lives along the seacoast, and may often 
be found abundantly in pools among the rocks when the 
tide is out. Two species are common along the Atlantic 
coast 

I. — Notice the general appearance of the animal — the 

spheroidal shape of the body, and the spines with 
which it is covered. See that one side is more flat- 
tened than the other; this is the oral surface, while 
the other is the aboral surface. 

II. — Examine the oral surface carefully. See the central 
mouth opening, with its five projecting calcareous teeth, 
and the more or less membranous area surrounding it ; 
this area is the peristome. See whether that part of 
the peristome next to the mouth opening is thickened. 
Find also the small calcareous ossicles which give 
strength to the membranous peristome. Make a draw- 
ing of the peristome and mouth. 

III. — Find along the outer margin of the peristome a great 
many of the movable ambulacra or tube feet, each end- 
ing in a sucker-like disk. Each of the ambulacra con- 
sists of a cylindrical basal portion, which in the living 



Branch Echinodermata 41 

animal can be greatly lengthened, and the disk-like tip 
by means of which it holds on to objects. Make a 
drawing showing the structure of the sucker-like tip. 
The flat central disk is supported by a calcareous plate. 

IV. — In addition to the numerous ambulacra on the outer 
margin of the peristome, find five pairs with somewhat 
larger tips surrounding the mouth. See between the 
pairs of ambulacra the groups of pedicellariae, appearing 
as miniature forceps on slender stalks. Are these 
present on other parts of the body ? 

V. — Find other ambulacra among the spines over the rest 

of the body. How generally are they distributed ? 

VI. — Extract at its base one of the long spines with which 
the body is covered. Study it with a hand lens and 
make a careful drawing showing the following parts : — 

a. The basal piece extracted from the body wall. 

b. The membranous part by which the spine is attached. 

c. The long spine proper, with its tapering surface 
fluted longitudinally. 

d. The flattened tip, with its polished tooth-like 
surface. 

VII. — Dissect out the flexible basal part of the spine to see 
the ball and socket joint. Make a diagrammatic sketch 
showing the structure accurately. 

VIII. — Describe the arrangement of the spines with ref- 
erence to the mouth, noting especially the differences in 
the length and the structure of the tips. 

IX. — Make a careful drawing of the spineless aboral area 
on the side opposite from the mouth. Show the four 
anal plates ; these form the periproct. 

X. — Study now a specimen on which the spines and soft 

parts have been removed by soaking for a few days in 
a strong solution of caustic potash. On the aboral sur- 



42 Laboratory Guide in Zoology 

face notice the space formerly occupied by the peri- 
proct. Notice that around it are five genital plates, 
each having a small hole near the apex ; these are the 
reproductive openings. See that one of the plates is 
larger than the others and is full of minute perforations ; 
this is the madreporic body. Make a drawing of the 
aboral surface of this specimen. 
XI. — Study the oral surface of the same specimen. Notice 
the large opening formerly occupied by the peristome. 
What shape is it ? Notice the five interradial sutures 
from the tip of each genital plate to the corresponding 
angle of the mouth pentagon. See the double rows of 
polished prominences for the attachment of the spines. 
See also the zigzag ambulacral suture running between 
each double row, and the double rows of ambulacral 
pores on each side of the double rows of spines. 

THE SEA-CUCUMBER 

The Holothurians or Sea-cucumbers are strange crea- 
tures that live in the ocean. They form a separate class 
(Holothuroidea) of the great group to which the starfish 
and sea-urchin belong. They have a water-vascular sys- 
tem similar in general to that of the starfish. 

I. — Make a drawing showing the general shape of the body 

and the position of the tentacles, as well as of the mouth 
and of the anal opening. 

II. — Describe the number, size, shape, and position of the 
tentacles. 

III. — Examine with a hand lens the ambulacral suckers with 
which the body is covered. Make a drawing of one of 
these, considerably magnified. Are these more abun- 
dant on the lower side of the animal ? On the upper 
side, are they more abundant near each end than in the 



Branch Echinodermata 43 

middle of the body ? Can you see that these ambulacral 
suckers are arranged in five broad bands ? 

IV. — Cut the body wall longitudinally on one side to lay 
open the central cavity. See the long much-coiled ali- 
mentary canal. Notice the structure of this canal; next 
the mouth is an oesophagus ; below this is a well-defined 
stomach; next comes the long, convoluted intestine, 
which is small in size throughout until it opens into 
the larger cloaca, at the posterior end. Make a sketch 
of the alimentary canal, labelling each part. 

V. — Remove the intestine, leaving the other parts of the 

canal intact. The most noticeable objects now visible 
are the genital gland, the respiratory tree, and the five 
sets of longitudinal muscles. 

VI. — The genital gland is near the middle of the upper half 
of the body cavity. It looks like a sort of brush, being 
composed of many slender filaments lying side by side. 
Notice that the duct leading from* these extends to an 
opening between two of the tentacles. (The genital 
gland may be the ovary or the testes, as the sexes are 
separate.) 

VII. — Trace out the two main divisions of the respiratory 
tree with their many branches. Notice the connection 
of each half with the cloaca. In this way fresh sea 
water reaches them. 

VIII. — Study the five sets of longitudinal muscles, extend- 
ing up and down the body walls. Trace these out 
carefully and describe them. Notice also the circular 
fibres which strengthen the body wall. 



44 Laboratory Guide in Zoology 

THE CLASSIFICATION OF THE ECHINODERMATA 

The starfish is perhaps the most typical representative 
of the branch Echinodermata, which includes also the sea- 
urchins, the sea-slugs or sea-cucumbers, the sea-lilies or 
feather-stars and the brittle-stars. In the members of this 
phylum the arrangement of the parts in a circle around a 
common centre is the most striking general character. 
This is obvious in the starfish, and may easily be seen in 
the other members of the group. There is also a calcare- 
ous outer skeleton which varies much in its texture, but 
the frequency with which it is furnished with spiny pro- 
jections led to the name Echinodermata. All members of 
the phylum live only in salt water. There are two open- 
ings to the alimentary canal. There is also a distinct 
nervous system, a circulatory system, a water system for 
locomotion, and other complicated organs. 

There are five principal classes of the Echinodermata, 
namely : — 

I. — Asteroidea. The starfishes are the typical representa- 

tives of this class. They abound in almost every sea, 
and may be found partly buried in the sand or con- 
cealed beneath the shelter of the rocks. As the name 
implies, they are star-shaped, generally with five rays. 
In color they vary considerably, but they are com- 
monly some shade of yellow, orange, or red. 

II. — Ophiuroidea. This class is made up of the peculiar 
sand-stars and brittle-stars, which have the arms longer 
and more distinctly separated from the central portion 
of the body than do the starfishes. 

III. — Echinoidea. The spiny sea-urchins form this group. 
In these the arms are absent, the body being rounded, 



Branch Echinodermata 



45 



and covered with a shell made up of closely united plates 
of a calcareous nature, to which stiff spines are attached. 
Sea-urchins live in rocky holes and crevices along the 
borders of the ocean, where they feed upon molluscs and 
seaweeds. Their mode of locomotion is similar to that 
of the starfish, although the movement is much slower. 

IV. — Holothuroidea. The strange sea-cucumbers or sea- 
slugs belong to this class. In these the body is elon- 
gated and covered with a thickened leathery wall. 
Around the mouth is a ring of tentacles. These slug- 
gish creatures live in the ocean, especially in tropical 
regions. 

V. — Crinoidea. The members of this class are commonly 

known as feather-stars or sea-lilies. They are com- 
paratively few in number, and for the most part being 
fixed to the bottom of the sea, they are seldom found. 
The star-shaped body is usually attached to a stalk. 
In former geologic times crinoids were very abundant; 
the formation of vast limestone areas is attributed to 
the gradual accumulation of their remains. 



CHAPTER VI 

BRANCH ANNULATA: THE TRUE WORMS 

THE EARTHWORM 

For the purposes of this study both living and dead 
earthworms should be provided. The larger the specimens, 
the more satisfactory will be the results. Kill some of the 
worms by enclosing them in a covered dish containing a 
little ether or chloroform. If the internal anatomy is to 
be studied in such freshly killed specimens, they should be 
dissected under water in a shallow dish having the bottom 
covered with wax or sheet cork. The internal anatomy 
may also be studied in specimens hardened in alcohol, 
although some of the more delicate parts are likely not to 
show so well as they do in fresh specimens. 

MOVEMENTS AND EXTERNAL ANATOMY 

I. — Place a living earthworm on a sheet of paper. 

Watch its movements. Determine which is the anterior 
end and which the ventral surface. Is it able to move 
backwards ? By what means does it move ? Is there 
a decrease in diameter when the worm stretches out ? 

II. — Find the bristle-like setae on the ventral surface. 
How many rows of them are there? Toward which 
end of the body do the tips of the setae point ? 

III. — Notice how the earthworm is divided into narrow 
rings, or segments, throughout its length. Study the 
first segment; the lip-like projection above the mouth 
is called the prostomium. 

4 6 



Branch Annulata 47 

IV. — A few segments back of the head find a ring-like 
swelling of the body : this is the clitellum. It is more 
prominent in some specimens than in others. 

V. — Examine the external surface carefully for openings 

through the skin. The mouth and anal openings are 
easily found. Find a small pore in the grooves between 

» successive segments behind the tenth along the mid- 
dorsal line ; these communicate with the body cavity 
and will sometimes emit a milky fluid when the animal 
is irritated. On the ventral side of the fourteenth seg- 
ment find two small openings, the external terminations 
of ducts leading from the ovaries. The external open- 
ings leading to the seminal vesicles will be found in the 
fifteenth segment. Draw a side-view of the earthworm. 

INTERNAL ANATOMY 

VI. — Pin the specimen to the bottom of the dissecting 
dish with its ventral surface downward, by inserting 
one pin through the prostomium and another through 
the posterior segment, stretching the body a little. 
With sharp-pointed scissors cut through the very thin 
body wall, near to and parallel with the dorsal median 
line. Be careful not to cut too deep. Notice the 
many transverse partitions joined to the inner surface 
of the body wall. Determine whether they correspond 
to the constrictions between the segments. Cut these 
partitions carefully down each side close to the body 
wall, and pin down the flaps of skin thus laid open. 

II. — The alimentary canal is now exposed. Notice that 
it passes directly through the partitions between the 
segments. See the dorsal blood-vessel along the top 
of the alimentary canal. Near the eighth and ninth 
segments, find branches running from this dorsal blood- 



48 Laboratory Guide in Zoology 

vessel around the alimentary canal to join the longi- 
tudinal ventral blood-vessel. These aortic arches form 
the centres of the blood system. 

VIII. — The most conspicuous bodies now exposed are the 
white-lobed seminal vesicles in the tenth and eleventh 
segments. They are connected by ducts with external 
openings on the ventral surface of the fifteenth seg- 
ment. 

IX. — The alimentary canal is composed of five parts, 
named as follows, beginning at the anterior end : 
pharynx, oesophagus, crop, gizzard, and intestine. Dis- 
tinguish each. The pharynx is continuous with the 
mouth and has light-colored muscular walls ; it extends 
to about the seventh segment. The oesophagus is a 
straight tube, generally extending from the eighth to 
the sixteenth segments. Near the sixteenth segment 
the alimentary canal is enlarged, forming a sort of thin- 
walled pouch ; this is the crop. Directly back of it is 
the muscular gizzard. The rest of the canal forms the 
intestine. Make a drawing of the canal. 

X. — Over the pharynx, near the anterior end, find two 

small white oval bodies, which form the central part of 
the nervous system : they are the cerebral ganglia. Re- 
move the intestine carefully, and find a white ventral 
nerve cord extending longitudinally. 

XI. — The ventral blood-vessel will be found extending 
longitudinally below the alimentary canal. It may be 
necessary to use another specimen in order to demon- 
strate it. 

XII. — Carefully push aside the alimentary canal from 
about the eighth to about the fourteenth segment. The 
very small white bodies to be seen in the base of the 
thirteenth segment are the ovaries. Near these are two 



_ 



Branch Annulata 49 

short funnel-shaped tubes, the oviducts, which pass 
through the partition to the fourteenth segment, and 
thence through the body wall to the outside. These 
furnish an exit for the contents of the ovaries. 

XIII. — Between the ninth and tenth, and between the tenth 
and eleventh segments, find two pairs of white pear- 
shaped bodies ; these are the seminal receptacles. 

XIV. — Beginning with about the fourth segment, find in 
the base of each segment except the last, and attached 
to the posterior surface of the septum in front, long, 
somewhat coiled, tubular organs. One end is free, but 
terminates in the next anterior segment by passing directly 
through the partition : the other end communicates with 
the exterior. These are excretory organs called nephridia. 
They are brought out distinctly by blowing alcohol upon 
them through the tube of a wash bottle. 

THE MARINE ANNELID 

(nereis virens) 

This curious worm lives in the mud along the seashore 
and the bottoms of tide marshes. It is of special interest 
because it shows a more highly differentiated structure than 
does the earthworm. 

I. — Study and describe the general shape of the body. 

What are the most important ways in which it differs 
from the earthworm ? How many segments are there ? 

II. — How do the appendages along the sides of the body 
compare with the segments in number ? Is it easier to 
distinguish the anterior and posterior ends than in the 
earthworm ? 

III. — Study the head : it has no appendages that project 
laterally from the sides, and is divided into two general 



50 Laboratory Guide in Zoology 

parts — a small anterior part, the prostomium, a large 
posterior part, the peristomium. Make careful draw- 
ings of the upper and lower views of the head and the 
first three segments back of it. 

IV. — Study the prostomium. Is it distinctly differentiated 
from the peristomium ? Notice the central lobe bear- 
ing in front the two club-shaped tentacles. Are they 
segmented ? See on each side of this central lobe the 
large conical palpi, distinctly segmented. Find the 
small black spots which are the eyes. How many are 
there ? 

V. — Study the peristomium : on each side in front are the 

two cirri, each double. Find the mouth. Sometimes 
this is extended and shows the two black, serrated 
mandibles. 

VI. — Study the lateral appendages of the body segments, 
— they are the parapodia. Are they of the same size 
throughout the length of the animal? Remove with 
forceps one of the parapodia, and examine it with a 
low magnifying power — a simple lens will do. Dis- 
tinguish two general parts — the dorsal and ventral 
lobes. On which is a large subtriangular blade — the 
gill ? Which bears the most spinose setae ? Treat a 
parapodium with caustic potash solution to bring out 
the spinose acicula. Make a careful drawing of a para- 
podium showing its parts and its basal connections. 

VII. — Lay the worm on the bottom of the dissecting tray, 
ventral side down. Cut longitudinally along the median 
dorsal line, and pin down the cut edges on each side. 
See how the body cavity is segmented. 

VIII. — Study the alimentary canal : see how the mouth 
opens into the pharynx, which in the living worm can 
be protruded ; and how the pharynx leads into the 



Branch Annulata 51 

oesophagus, and the latter into the long intestine which 
extends to the posterior end. Can you see a small gland 
on each side of the oesophagus ? Where do these glands 
empty ? Do the constrictions of the intestines corre- 
spond to the divisions of the segments ? Notice the 
mesentery below the intestines, binding it to the body 
wall. The mesentery of the upper part was probably 
destroyed when the body was cut open. 
3 IX. — Cut open the pharynx : notice the powerful muscles 
and the two conspicuous black teeth which may be 
seen on the outside in those specimens in which the 
pharynx is protruded. 
X. — Trace out as well as you can the blood-vessels and 
the nerve system. 



52 Laboratory Guide in Zoology 

THE CLASSIFICATION OF THE ANNULATA 

The earthworm is a typical representative of the phylum 
Annulata, nearly all the members of which have an elon- 
gate body divided into numerous segments, with an internal 
partition between each of the segments. There is a well- 
developed alimentary canal, a distinct body cavity, a system 
of blood-vessels, and a nervous system with cerebral 
ganglia and ventral nerve cord which is double, and gener- 
ally shows a series of ganglia along the segments. The 
members of the phylum also have nephridia, or pairs of 
tubes leading from the body cavity through the body wall 
and serving as organs of excretion. 

This phylum is divided into four classes, namely : — 

Class I. Chaetopoda. The Earthworm and Nereis. 

Class II. Gephyrea. 

Class III. Archi-annelida. Polygordius and its Allies. 

Class IV. Hirudinea. The Leeches. 

Of these four classes the first and fourth contain the most 
generally known members of the branch. The second 
class, Gephyrea, is exceptional in its characters, in that the 
members of it are not segmented when adult, although they 
show the segmented condition during their development. 



CHAPTER VII 
BRANCH ARTHROPODA: ANIMALS WITH JOINTED LEGS 
THE WOOD-LOUSE OR SOW-BUG 

These curious creatures may be obtained in abundance 
under boards and stones, especially in moist situations. 
For this study, get as large specimens as you can find. 

I. — Notice the segmented character of the body. See if 
you can easily distinguish the three divisions of the 
body — head, thorax, and abdomen. 

II. — When the animal is viewed from above, the head is 
what appears to be the first segment. Determine the 
limits of the head by looking at it from both sides. 
Notice its mode of attachment to the first segment of 
the thorax. 

III. — To distinguish between the thorax and abdomen, look 
for a place where there is a decided difference in the 
size of two adjoining segments as seen from above. 
How many segments has the thorax ? How many has 
the abdomen ? 

IV. — Returning now to the head, study the long, jointed 
antennae. Compare the segments of these with the seg- 
ments of the legs. Is there a similarity ? Notice the ag- 
gregation of simple eyes near the base of each antenna. 

Unless the specimens are quite large, the mouth parts 
are not easily distinguished by beginners. The jaws, 
maxillae, and upper and lower lips come close together in 
a point. The tips of the jaws are black. 

53 



54 Laboratory Guide in Zoology 

V. — How many legs has each segment of the thorax ? 

Make a drawing of one of the legs as it appears under 
the lens, showing distinctly in the drawing the parts of 
which it is composed. In female specimens, there is a 
thin membrane or covering — the egg pouch — on the 
ventral surface of the thorax at the bases of the legs. 

VI. — Study the plate-like gills on the ventral surface of the 
abdomen. Why should these creatures be found only 
in moist situations ? 

THE LOBSTER, OR CRAYFISH 

The lobster is one of the most satisfactory animals to 
study. It is better to have fresh specimens that have not 
been boiled, but if these are not easily obtainable, boiled 
specimens may be substituted. In regions where cray- 
fishes are abundant, these may be used instead of the 
lobster. 

EXTERNAL ANATOMY 

I. — Does the lobster show a more marked bilateral sym- 

metry than the earthworm ? Study the hard, strong 
covering of the body ; this is a true outer skeleton or 
exoskeleton. Notice the soft, pliable places in the 
skeleton which permit the bending of the body. These 
places differ from the rest of the skeleton only in 
having no calcium. 

II. — Axial Arrangement. In the axial arrangement of 
parts what resemblances can you find between the 
earthworm and the lobster? Both have a ringed or 
segmented structure, but in the lobster this is shown 
only in the posterior part of the body. Notice that 
the body axis is separated into two great divisions. 
The anterior one includes the head and thorax, closely 
united, and is called the cephalothorax. The posterior 



Branch Arthropoda 55 

division comprises the remaining part of the animal, 
and is called the abdomen. Fix carefully in mind the 
precise boundary of these two great divisions, by bend- 
ing the abdomen back and forth to see its mode of union 
with the cephalothorax. The broad, unsegmented cov- 
ering of the cephalothorax is the carapace, and its 
toothed projection between the eyes is the rostrum. 
Near the middle of the carapace find a distinct trans- 
verse suture ; this represents a somewhat indistinct divi- 
sion between the head and thorax, and for that reason 
is called the cervical suture. 

III. — Abdominal Somites. Find the seven distinct ring- 
like segments, or somites, that form the abdomen. In 
any single somite distinguish the following parts : 
(1) The broad, dorsal part is the tergite. (2) The nar- 
row, ventral part of the ring is the sternite. (3) The 
pointed, somewhat curved part which forms each side 
is the pleurite. Notice how the seventh, or the last, 
segment, the telson, differs from the others. 

IV. — Abdominal Appendages. On the sternite of each 
segment find a pair of jointed movable organs, the 
swimmerets. Examine a single one of these, and find 
that it is made up of a basal part, the protopodite and 
two branches ; the outer branch is the exopodite and 
the inner branch is the endopodite. Examine other 
swimmerets to confirm this structure. Those of the 
first and second abdominal segments are usually modi- 
fied, and in the female are sometimes wanting. The 
swimmerets of the sixth segment are so much enlarged, 
and so like the hard parts of the skeleton, that they 
will not at first be recognized as swimmerets. The 
exopodites and endopodites of these swimmerets to- 
gether with the telson form the tail fin of the lobster. 



56 Laboratory Guide in Zoology 

V. — Somites of the Cephalothorax. From a ventral view 

notice how small are the sternites of the thoracic seg- 
ments. This is caused by the enlargement of the 
basal joints of the appendages. The unbroken sides 
of the carapace represent the united pleurites of the 
various thoracic somites. Follow carefully the irregu- 
lar outline of the carapace, and indications of the seg- 
mented structure will be seen. In general it may be 
said that each pair of limbs on the cephalothorax repre- 
sents a single somite. 

VI. — Appendages of the Cephalothorax. Study carefully 
the following parts : — 

a. The four posterior, nearly uniform, appendages are 

the legs used for walking. 

b. The much larger pair, just anterior to these, are 

used for capturing and crushing food, and are called 
chelae. 

c. Directly in front of the chelae find three pairs of 

appendages drawn closely to the body. These are 
of the nature of legs, but since they serve to pre- 
pare the food for the mouth, they are called 
maxillipeds. 

d. The two appendages directly anterior to the maxilli- 

peds are the true maxillae. Notice the scoop-like 
structure held by the second maxilla : it is called the 
gill scoop. 

e. In front of, and beneath the maxillae, are the hard- 

toothed jaws, or mandibles. Move them back and 

forth to see their mode of action. Is it from side 

to side, or up and down ? 
/. The long tapering structures with large basal segments 

are the antennae : they serve as organs of touch. 
g. The somewhat similar, but two-branched and shorter, 



Branch Arthropoda 57 

pair directly in front of the antennae are the anten- 
nules, serving the same function as the antennae and 
probably that of smell. Each also contains in its 
basal part an organ of equilibration. 
//. The jointless stalks protruding from either side of 
the rostrum are the eye-stalks, tipped with the 
eyes. Examine them to learn the field of vision pos- 
sessed by the lobster. 
VII. — Breathing Apparatus. With strong scissors remove 
one side of the carapace. The light-colored, many- 
lobed organs thus exposed are the gills, or breathing 
apparatus of the lobster. They are bathed in the water 
that flows under the overhanging carapace. Move the 
legs back and forth, and see the relation between the 
legs and gills. Move the maxilla to which the gill- 
scoop is attached, and observe how a stream of water 
may thus be made to pass under the carapace. The 
blood passes through the gills, thus coming into very 
close contact with the water, to which it gives up its 
carbonic acid and from which it receives its oxygen. 
VIII.— External Openings. Find the mouth, tightly cov- 
ered by the mandibles and maxillae. On the ventral 
side of the telson, find a short longitudinal slit, the anal 
opening. Examine the basal segments of the third and 
fifth legs, to find the small external openings of the 
reproductive organs. Those of the female will be 
found in the basal segments of the third pair, and those 
of the male in the basal segments of the fifth pair. But 
one kind of reproductive organs will be found in an 
individual. Compare this with the case of the earth- 
worm. On the basal segment of each of the antennae 
find a single small opening, the outlet of the excretory 
organs. On the upper surface of the basal segment 



58 Laboratory Guide in Zoology 

of each of the antennules find a peculiar structure, 
the organ of equilibration. 

IX. — Comparison of Appendages. Remove one of the 
chelae, study and number its parts. Remove, study 
in the same way, and compare with the chelae, one of 
the first or second walking legs. Go through the same 
process with one of the fourth walking legs. Review 
the entire row of appendages, and note that all are in 
pairs, and that they are nearly all jointed, and possess 
branched terminations. Regarding each pair of ap- 
pendages as representing a single somite, determine the 
number of somites of which the lobster may be said to 
be made up. Draw a side view of the animal. 

INTERNAL ANATOMY 

X. — Muscular System. Remove, with strong knife or scis- 

sors, the tergites of the abdominal segments, cutting 
away the muscles attached to them. The white masses 
filling the abdomen are the strong muscles, and form 
the edible flesh of the lobster. 

XI. — Blood System. Remove in a similar manner the 
entire top of the carapace, being very careful to dis- 
turb none of the organs below. Near the centre of 
the thorax, find exposed a soft, plastic, somewhat angu- 
lar body, the heart. Find the colorless, hence some- 
what indistinct, arteries, running forward, laterally, and 
backward from the heart. Follow the artery running 
backward, by pushing aside the muscles between which 
it lies, and observe its branches supplying the surround- 
ing tissues. The straight tube below, and attached to 
the blood-vessel, is the intestine. 

XII. — Reproductive System. Carefully remove the heart, 
and find directly below it either the testes or the ova- 



Branch Arthropoda 59 

ries. The testes are a pair of three-lobed bodies, gen- 
erally white. If testes are present, find the ducts 
leading from them to the external openings which 
have already been found. The ovaries are a pair of 
long, two-lobed bodies. If these are present, find their 
ducts. Remember that only ovaries or testes will be 
found in an individual, never both. 

XIII. — Digestive System. Remove the reproductive 
organs, and the most conspicuous portion now ex- 
posed will be the digestive glands. Find the ducts by 
which their contents are emptied into the small intes- 
tine. The stomach is the hard-walled receptacle just 
in front of these glands. It passes anteriorly into the 
oesophagus, and posteriorly into the small intestine. 
Pass the forceps through the mouth into the oesopha- 
gus, and watch its passage to the stomach. The 
very short small intestine expands into the large intes- 
tine which terminates in the anal opening in the telson. 
Remove the stomach and open it, to find an apparatus 
for crushing the food. Make a sketch of the digestive 
system. 

XIV. — Nervous System. Beginning with the posterior 
part of the abdomen, carefully remove the body 
muscles from the abdomen and thorax. Left plainly 
exposed between the muscles will be found the nerve 
cord with its branches. Follow that forward to the 
head. In the thorax it enters a hardened passage, 
to remove which will require some care. Just posterior 
to the oesophagus, find a large ganglion into which the 
nerve passes. Find a similar ganglion in front of 
the oesophagus. You may be able to see how these 
are connected by the nerve cord passing around the 
oesophagus. 



60 Laboratory Guide in Zoology 

The fact that the digestive canal passes at its ante- 
rior end through a ring of the nervous system is an 
important characteristic of animals below the verte- 
brates, or back-boned animals. Find, if you can, nerves 
passing from the forward ganglion to the eyes, antennae, 
and antennules. Make a sketch of the nerve system. 

XV. — Excretory Organs. Directly under the antennae, see 
the green bodies, the excretory glands, whose openings 
are found in the basal segments of the antennae. 

XVI. — Compare the structural plan of the lobster with that 
of the earthworm, remembering that both are analogous 
to a tube within a tube, the edges of both tubes being 
united at both ends. With this structure in mind, tell 
which tube the mouth and the anal opening are con- 
nected with. In which tube do the reproductive and 
excretory organs lie ? Where do their ducts lead ? In 
which tube does the liver lie, and into which do its 
ducts pass ? What is the relation of the skeleton and 
body muscles to the system of tubes ? 



THE COMMON CRAB 

Crabs are familiar to all who have wandered along the 
sea-shore at low tide. They run sideways over the exposed 
rocks, or crawl leisurely along the bottoms of the pools. 
They are closely related to the lobster, although very dif- 
ferent in appearance. 

I. — Study the body as to its general shape. What modifi- 
cations in the size, shape, and arrangement of the 
cephalothorax and abdomen make it appear so different 
from the lobster ? Where is the abdomen situated ? 
Draw the view presented as you look down upon the 
back. 



Branch Arthropoda 61 

II. — Study the carapace. Is its front margin denticulate.? 
Are there any sutures ? Distinguish these parts, which 
are marked off by the sutures : — 

a. The gastric lobe, a large, elevated, subtriangular 
area in the middle of the front half. 

b. The cardiac lobe, a somewhat similar area, back of 
the gastric lobe. 

c. The hepatic lobes, one on each side of these median 

lobes. 

III. — Study the ventral surface; make a drawing of it. 
See the large plastron which forms the under side of 
the body. Notice the plates of which it is composed. 
Notice the broad groove in which the abdomen rests. 
In male specimens the abdomen is narrow ; in female 
it is broad and rounded, its concave ventral surface 
forming a chamber in which the eggs may be carried. 
How manv segments in the abdomen ? 

IV. — Study the six pairs of appendages attached to the 
sides of the plastron. Beginning posteriorly, find four 
pairs of walking legs, one pair of large chelae, and one 
pair — the third — of maxillipeds. Are the appendages 
similar in general structure to those of the lobster? 
Study the appendages of the head. 

V. — Immediately in front of the third pair of maxillipeds 

are the second and first pairs of maxillipeds. In front 
of the latter are the large mandibles. Find the eyes. 
How are they situated ? Find the antennules and the 
antennae. 

VI. — Find a large orifice on each side of the head, opening 
into the branchial chamber. Notice a membranous 
flap on each side. See if this is a part of the second 
maxilliped. 

VII. — Should you say that the crab is to be placed higher 



62 Laboratory Guide in Zoology 

in the scale of classification than the lobster ? Does it 
show greater differentiation in its structure ? 

THE CYCLOPS 

The Cyclops is a microscopic crustacean of the same 
class to which the lobster belongs. It may be found in the 
water of almost any aquarium where aquatic plants have 
been growing ; it appears to the naked eye as a small white 
speck swimming rapidly about with a peculiar, jerky move- 
ment. The large specimens usually found are females. 
The males are much smaller, and generally are less abun- 
dant, and therefore are not so well adapted to study. Pre- 
paratory to a study with a low power, several specimens 
should be removed from the culture jar to a watch glass. 
To do this, place a finger on the end of a short glass tube, 
and inserting the other end in the water as near the speci- 
men as possible, remove the finger; the animals will be 
drawn into the tube with the surrounding water, and by 
again covering the exposed end of the tube they may be 
transferred to a watch glass. If a little ether is placed in 
the water containing the animals, their rapid actions will 
be checked, giving a better opportunity for observation. 
Place the watch glass on the stand of the microscope and 
study with the low power. 

I. — Dorsal View. By careful manipulation, find a specimen 
showing a good dorsal view. Observe the oval body, 
tapering rapidly toward the posterior end. Study the 
segmentation of the body axis; since the head and 
thorax are united, as in the lobster, the body axis may 
be divided into the two great divisions, — the cephalo- 
thorax and abdomen. The cephalothorax is composed 
of the first five segments beginning with the anterior 



Branch Arthropoda 63 

end. The remaining tapering segments make up the 
abdomen. Observe the broad dome-shaped carapace 
making up the anterior part of the cephalothorax. 
Compare this with the carapace of the lobster in posi- 
tion and shape. If the specimen is a female, a pair of 
egg sacs may be seen attached to the first abdominal 
segment. Study the greatly developed posterior seg- 
ment of the abdomen, with its branched projections. 
Observe the yellow outline of the intestine showing 
through the wall of the abdomen. Dark masses show- 
ing through the carapace are the reproductive organs. 
Near the anterior edge of the carapace on the median 
line, find the dark purple eye-spot : this is really made 
up of two disks which may be seen with the high 
power. 
, — Lateral or Ventral View. Obtain a good lateral or 
ventral view, if necessary using the needles in manipu- 
lation. The most noticeable appendages of the cephalo- 
thorax are the long-jointed antennae. Just back of 
these another smaller pair, the antennules, may be 
found. Just below the two pairs of antennas the 
mouth parts surrounding the mouth are grouped, 
although it may be quite difficult to distinguish clearly 
the pair of mandibles and the two pairs of maxillae. 
At some distance behind the mouth parts are the four 
pairs of thoracic appendages, the legs. Study the 
segmentation of the legs, and try to make out a fifth, 
rudimentary pair. 



64 Laboratory Guide in Zoology 

THE FLATTENED CENTIPEDE, OR THOUSAND-LEGS 

The common " thousand-legs," or centipedes, are found 
under boards and logs. For this study those with flattened 
bodies should be selected. 

I. — Observe the jointed nature of the body. See that the 

head is easily distinguishable. Is there any distinct 
division between thorax and abdomen ? From a dorsal 
view, count the segments back of the head. Are all 
the segments of the same size ? 

II. — Count the pairs of legs. Does each segment bear 
one or two pairs ? Study the legs carefully. Are 
they jointed ? If so, how many segments has each ? 

III. — Find the breathing pores, or spiracles: one on each 
side of a segment, just above the coxa, the first leg- 
joint. 

IV. — Examine the antennae — the most noticeable append- 
ages of the head. Directly behind the antennae find 
the eyes — blackish clusters made up of many ocelli, 
or single eyes, crowded near together. 

V. — Directly in front of the base of the antennae, find 

two pairs of mouth parts, or jaws, one pair being much 
smaller than the other. But first distinguish carefully 
the front pair of legs, so much modified that they look 
like sharp claws. In poisonous species the poison is 
secreted in these claws. 

VI. — Make a good-sized sketch of the centipede as seen 
from the dorsal side, and another of the head as seen 
from the ventral side. 



Branch Arthropoda 65 

THE LOCUST, OR GRASSHOPPER 

Collect as large specimens as you can find. Have the 
dead grasshopper pierced with a pin or held with small 
forceps so that the examination may be quickly and easily 
made. Examine first with the naked eye, and then with a 
hand lens or a dissecting microscope. 

I. — Take a general but careful view of the external feat- 

ures of the grasshopper. Lift the wings ; note their 
number and place of attachment. Observe the num- 
ber of pairs of legs and the location of the anterior 
and posterior pairs. 

II. — There are three principal divisions of the body, — 
head, thorax, and abdomen. Move the head gently 
from side to side to see the line of division between it 
and the rest of the body. Examine the long tapering 
posterior part of the body : this is the abdomen. 
Between it and the head lies the third great division 
of the body, — the thorax. The anterior margin of the 
thorax passes directly in front of the first pair of legs, 
and the posterior boundary is just back of the third 
pair of legs. Study the thorax carefully, remembering 
that the two pairs of wings and the three pairs of legs 
are all attached to it. 

III. — You have already noticed that the abdomen is 
divided into segments, or somites, in a way some- 
what similar to the abdomen of the lobster, but 
with less freedom of motion. Look for a similar but 
less marked series of divisions in the thorax. There 
are really three segments in the thorax, each bearing 
a pair of legs. See the first of these, — the prothorax, 
— easily distinguished by the separation from the head 
in front and from the rest of the thorax behind. The 



66 Laboratory Guide in Zoology- 

second and third divisions are not so well defined, 
and do not move upon each other. The division may 
be made out, however, by observing certain lines which 
represent the union of the two. On the ventral surface 
this line will be found behind the second pair of legs; 
trace it up along the sides and back. The middle seg- 
ment thus distinguished is the mesothorax, and the hind 
segment is the metathorax. 

IV. — Notice that the position of the head is at right 
angles to the body axis. Compare it in this respect 
with the lobster. Study the long slender projections 
— the antennae, or feelers — on the front of the head. 
See with a lens their jointed structure. Notice the 
peculiar surface of the large compound eyes. Between 
the compound eyes, find three small ocelli, or simple 
eyes. 

V. — Begin the study of the mouth parts by finding on the 

lower side of the face a movable flap — the labrum, or 
upper lip. Observe this carefully, then remove it and 
see directly beneath it the mandibles, or jaws, — one on 
each side; these are hard, black, toothed structures. 
Press them apart, and then pull them out carefully with 
pointed forceps. You thus bring into view a dark brown, 
spindle-shaped organ in the centre of the mouth : this 
is the ligula, or tongue. The entrance to the gullet is a 
small round opening above the base of the tongue. 
Below where the mandibles were, the maxillae are now 
to be seen, one on each side. Pull one of these out, 
being careful to get the whole of it, and by the aid of 
a lens identify the following parts : — 

a. The basal segment. 

b. The jointed appendage on the outside, called the 
maxillary palpus. 



Branch Arthropoda 67 

c. The large thin plate-like blade. 

d. The more slender inner portion, which is the true 
maxilla. 

e. Directly below the maxillae lies the labium, or lower 
lip. On each side a palpus is attached : these are 
the labial palpi. 

Make good-sized drawings of each of the mouth parts, 
labelling each. 

VI. — Observe carefully the general nature of the legs 
and their attachment to the body. Remove one of the 
front legs and identify the following parts : the coxa, 
the short segment next the body ; the trochanter, a short 
segment connecting the coxa with the femur, the first 
long segment ; beyond the femur is another long seg- 
ment, the tibia, which articulates with the tarsus, or foot, 
a series of short segments, the last of which is tipped 
with claws and has peculiar pads on its under surface. 

VII. — Remove one of the hind legs and make a careful 
drawing showing each of its parts. Why should the 
femur and tibia be so much longer in these legs than in 
the front and middle pair ? 

VIII. — Carefully turn back the outer pair of wings. Note 
that they are the anterior pair. To which division of 
the thorax are they attached ? Lift one of the under 
wings and notice its attachment to the thorax. Spread 
it out and observe its fan-shaped appearance. See that 
it is composed of a membrane stretched over a frame- 
work of veins. 

IX. — On each side of the mesothorax, over the second pair 
of legs, find the spiracle, a slit-like opening to the air- 
tubes. Find another spiracle on the prothorax. 

X. — Bend the abdomen and notice the play of the seg- 

ments upon each other. Theoretically each segment 



68 Laboratory Guide in Zoology 

is divided into four parts : the tergite is the dorsal 
portion, a pleurite is on each side, and the sternite forms 
the ventral surface. See if you can distinguish these 
parts. Remember the structure of the segments in the 
lobster. 

XL — Study the first segment; that is, the one next to the 
thorax. Its sternite is not easily seen, but on each side 
above you will find a nearly circular cavity covered by 
a thin membrane. This structure is believed to serve 
as an ear. On the side of the abdominal segments 
find spiracles similar to those on the thorax. Are spir- 
acles found on all of the segments? Is there more 
than one pair on any somite ? 

XII. — Notice that the somites at the posterior end of the 
abdomen are greatly modified. In the case of female 
specimens the abdomen ends in two pairs of pointed 
processes curving outward. When these are brought 
together they form a device for burrowing into the 
ground, and they serve as the ovipositor of the insect. 
In the male the end of the abdomen is much blunter. 

XIV. — Draw a side view of the grasshopper. 

THE DRAGON-FLY 

Dragon-flies are abundant about ponds in summer. 
Large specimens serve admirably for showing the general 
structure of an insect. 
I. — Find the three great divisions — head, thorax, and 

abdomen — into which the body axis is separated. 

II. — Compare the relative sizes of each of these divisions 
with the relative sizes of the same parts in the grass- 
hopper. 

III. — Between which parts does the division line show 
most plainly ? 



Branch Arthropoda 69 

IV. — Notice that the head, convex in front and concave 
behind, is given its peculiar shape by the very large 
compound eyes. 

V. — Using the lens, find the short antennae. How many 

segments has each ? 

VI. — Near the base of the antennae find two small simple 
eyes, the ocelli. 

VII. — Find a third ocellus between and above these two 
ocelli. 

VIII. — Notice a slight projection covered with hairs, 
sheltering the ocelli. 

IX. — In examining the mouth parts, first observe the large 
size of both upper and lower lips. 

X. — Push these parts aside so that the mandibles — the 

large toothed jaws — may be seen. Find beneath the 
mandibles another pair of jaws, the maxillae; these 
consist of several parts, as in the grasshopper, and 
should be carefully removed and studied under the 
microscope. 

XI. — Examine the thorax carefully, to find its three 
segments, — the prothorax, the mesothorax, and the 
metathorax. The lines of division may most easily 
be seen on the ventral surface. Remember that each 
of these divisions bears one pair of legs. 

XII. — Note the relative size of the thoracic segments. 
The enlargement of which one gives the insect its 
peculiar hunchbacked appearance ? 

XIII. — Demonstrate the truth of the statement that the 
anterior and posterior pairs of wings are attached to 
the mesothorax and metathorax respectively. Reflect 
upon the attachment of the wings in the other insects 
studied, and remember that the place of attachment is 
constant. 



JO Laboratory Guide in Zoology 

XIV. — Note the structure and size of the dragon-fly's wings 
as compared with those of other insects. Notice the 
relative size of the front and hind wings. What bear- 
ing do these characters have upon the habits of life of 
the dragon-fly ? 

XV. — Study the veins of the wings. Near the middle of 
the front margin find a slight notch connected with a 
short transverse vein. This structure is called the 
nodus. Its presence is an important characteristic of 
this group of insects. 

XVI. — Notice the legs. Are they large or small ? Does 
the dragon-fly walk much ? 

XVII. — Beginning with the segment next the body find 
the following parts of one of the legs : coxa, trochanter, 
femur, tibia, and tarsus. 

XVIII. — Study the claws on the tarsus. To what special 
use are they likely to be put ? 

XIX. — Find the ten segments which compose the abdo- 
men. The division between the segments is indicated 
by ridges which completely surround the joints. Bear 
this in mind when determining the segments nearest the 
thorax. 

XX. — In any single segment point out the parts, called 
the tergite, pleurite, and sternite. (Refer if necessary 
to page 68.) 

XXI. — Find the spiracles, or breathing pores, on the pleu- 
rites. What is their position ? 

XXII. — Study the terminal segment. In the female this 
segment is large and rounded ; in the male it has four 
pointed appendages. 

XXIII. — Make a drawing of a dragon-fly as seen from 
above. 



Branch Arthropoda 71 






THE BUTTERFLY 



Before mutilating the specimen, study carefully its gen- 
eral structure. Notice the relative sizes of the wings and 
body, the markings on the wings, and the hairy covering 
of the body. 
I. — Note the relatively large size of the compound eyes ; 

examine the outer surface of one with a lens to see its 

honeycomb appearance. 
II. — Are there any ocelli ? If so, where are they situated ? 

III. — Examine the antennae. What is the general shape ? 
About how many segments are there in each ? Which 
segments are the longest ? How does the basal seg- 
ment differ from the others ? 

IV. — Notice the long coiled sucking organ — the proboscis 
— at the mouth. Is it composed of one or two pieces ? 
Notice the two jointed hairy organs beside the probos- 
cis : these are the labial palpi. The proboscis is formed 
of the modified maxillae. 

V. — Notice the small thorax in close connection with the 

head. Compare the connection with that found in the 
dragon-fly. 

VI. — Observe the large mesothorax bearing the front pair 
of wings. Find the suture between it and the meta- 
thorax which bears the posterior wings. 

VII. — Notice the fragility of the legs. Give a reason for 
their small size as compared with those of the grass- 
hopper. 

VIII. — Are the front legs as large as the others ? When 
you have a chance to see a large butterfly walking, see 
how many feet it uses. 

IX. — Place a piece of the wing under the low power of 
the microscope. Observe the shingle-like arrangement 



J2 Laboratory Guide in Zoology 

of the scales. What difference is to be seen at the edge 
of the wing ? 

X. — Scrape off a few of the scales on a glass slide and 
study with the high power of the microscope. Notice 
the structure and the difference in shape. Draw five 
specimens, each different from the others. 

XL — Scrape off a few of the hair-like scales from the 
thorax and study them in the same way. Can you find 
any scales intermediate between the short, broad ones 
and the long, hair-like ones ? 

XII. — Count the abdominal segments. If necessary, 
remove some of the hairy covering to show the joints. 

XIII. — Rub off the scales from the sides of the body 
and find the spiracles. How many are there ? 

XIV. — Is each segment made of four parts — tergite, two 
pleurites, and sternite — as in other insects ? 

XV. — Make a drawing of the butterfly as seen from above 
when its wings are expanded. 

THE SPIDER 

I. — Segmentation of the Spider. Notice how the body axis 
is divided into two great divisions by a deep constric- 
tion near its middle. The anterior division is made 
up of the head and thorax, and is called the cephalo- 
thorax. The posterior division is the abdomen. How 
does this division of the body axis compare with that 
of the lobster ? Notice the entire absence of any 
segmentation either in the thorax or abdomen. 

II. — Appendages of the Head. The parts of the head 
must be studied with the low magnifying power. Are 
there any antennae ? Scattered over the anterior part 
of the head find the small black ocelli, — generally four 






Branch Arthropoda 73 

pairs. Directly below the eyes is the pair of broad, 
thick mandibles, or jaws. Find a sharp-pointed claw- 
on the tip of each mandible. It is within these claws 
that the poison glands are situated. Directly below the 
mandibles is another pair of jaws, or maxillae. The 
maxillae themselves are short and thick, but each pos- 
sesses a long jointed appendage, or palpus, which looks 
very much like a foot. See the mouth between the 
pair of mandibles and the pair of maxillae. 

III. — Appendages of the Thorax. The thorax bears four 
pairs of legs, a number characteristic of spiders. The 
maxillary palpi just mentioned, though smaller than the 
legs, are sometimes taken for a fifth pair of legs. See 
that this point is clearly understood. Determine the 
number of segments in the legs. Beginning with the 
one next the body, they are coxa, trochanter, femur, 
patella, tibia, metatarsus, and tarsus. The trochanter 
and patella are generally very small. 

IV. — Appendages of the Abdomen. Near the posterior end 
of the abdomen, notice a blunt bunch of finger-like pro- 
jections, the spinnerets, usually six in number. To see 
them well it will be necessary to use a low magnifying 
power. The spinnerets are the organs that form the 
spider's silken thread. In the end of each spinneret 
there are a great number of small tubes. A peculiar 
fluid is forced out through these tubes which hardens as 
soon as it strikes the air, thus forming the silk thread. 

Try to find a hard rough structure surrounding a 
pore or spiracle just in front of the spinnerets. This 
opening leads to a breathing apparatus. Two small 
openings to another breathing system may be found on 
the ventral side of the abdomen, near its union with 
the thorax. 



74 Laboratory Guide in Zoology 

THE CLASSIFICATION OF THE ARTHROPODA 

The branch Arthropoda which includes the jointed-footed 
animals, is one of the largest and most important zoolog- 
ical divisions. Its members differ from the Annulata in 
having jointed legs or other appendages attached to the 
body segments, and from the Mollusca in having the body 
definitely divided into segments. They have an exoskel- 
eton composed of chitin or of chitin and calcium combined. 
They possess a specialized nervous system, composed of a 
dorsal brain and a double row of ganglia along the ventral 
side of the body cavity. In general, the body is bilaterally 
symmetrical. 

The following classes of Arthropoda are now recognized 
by leading authorities : — 

Class I. Crustacea. Lobsters, Crabs, Shrimps, and 
Barnacles. 

Class II. Onychophora. Peripatus. 

Class III. Myriapoda. Centipedes and " Thousand-legs." 

Class IV. Insecta or Hexapoda. Bees, Beetles, Butter- 
flies, and other insects. 

Class V. Arachnida. Spiders, Scorpions, and Mites. 

The first class, the Crustacea, includes the smallest as 
well as the largest forms of the Arthropoda ; forms which 
vary in size from the microscopic Cyclops to the huge 
crabs, some of which are of enormous size. The typical 
crustacean is made up of twenty-one segments, divided 
between the three great divisions of the body, — head, 
thorax, and abdomen. The segments of the head and 
thorax have become united, forming the cephalothorax, 
while the individual segments of the great divisions of the 
body have become so fused together that it is difficult 
to distinguish the typical number. There are two pairs 



Branch Arthropoda 75 

of antennae, the smaller of which are called antennules. 
The body is covered with a chitinous integument, a large 
part of which is usually hardened with lime. This cover- 
ing is cast off at frequent intervals during the growth of 
the animal. During development many crustaceans pass 
through a series of peculiar changes of form which are 
called metamorphoses. Nearly all are water breathers ; 
some live in fresh water or in moist situations on the 
land, but the great majority are marine. 

The second class, Onychophora, includes only the single 
remarkable genus Peripatus. The members of this genus 
are peculiar creatures, which appear to be a connecting 
link between the Annulata and the Arthropoda. Only 
a few species are known, all inhabiting tropical regions. 

The members of the third class, Myriapoda, have a dis- 
tinct head, but the segments of the thorax and abdomen 
form a continuous series. The number of these segments 
is indefinite. Each bears one or sometimes two pairs of 
legs. They breathe air by means of tracheae. The centi- 
pedes and millipedes or " thousand-legs " are typical rep- 
resentatives of this class. 

The fourth class, Hexapoda, differs from the preceding 
classes in having three distinct divisions of the body, — 
head, thorax, and abdomen. The head is composed of several 
united segments ; the thorax of three segments ; and the 
abdomen of from seven to eleven segments. There are six 
legs, one pair being borne by each thoracic segment. The 
thoracic segments also bear on their dorsal surface one or 
two pairs of wings. The nervous system has a wonder- 
fully complex specialization, furnishing the insect with 
great instinctive powers. Growth takes place only during 
the early or larval life, and in many forms complicated 
transformations occur. 






-j 6 Laboratory Guide in Zoology 

The class Arachnida includes the spiders, scorpions, 
and mites. In these there are two chief divisions of the 
body, — the cephalothorax and abdomen, eight legs, no 
antennae, and generally no distinct transformations. With 
unimportant exceptions they breathe air either by means 
of tracheae or of book-lungs, and have a varying number 
of simple eyes upon the cephalothorax. 



CHAPTER VIII 

BRANCH MOLLUSCA: THE OYSTER, CLAMS, AND THEIR 

ALLIES 

THE FRESH-WATER CLAM 

EXTERNAL ANATOMY 

I. — Place a clam in a glass of tepid water and observe 

the gradual opening of the shell, and the protrusion 
from one end of a white, blunt, muscular projection, 
the so-called foot. This marks the anterior end of 
the animal, and by its protrusion and retraction the 
clam steadily moves along the sand, leaving grooves 
made by the sharp edges of the shell. In removing 
the creature from the water in preparation for the 
study of its structure, notice how the two halves of the 
shell are quickly brought together and the foot with- 
drawn. 

II. — The lateral surfaces are easily distinguished. They 
are the broad oval surfaces upon which the clam rests 
when placed upon the table. The sharp edges of the 
two parts of the shell form the ventral surface. It is 
this surface that makes the groove markings in the 
sand, mentioned above. The opposite thicker edge is 
the dorsal surface. 

III. — With a clear idea of the lateral, dorsal, and ventral 
surfaces in mind, determine the anterior and posterior 
ends by the aid of the following directions. On the 

77 



78 Laboratory Guide in Zoology 

dorsal surface find two prominences, the umbones, near 
together. Notice that the umbones are nearer one 
end than the other. The end to which they are nearer 
is the anterior end, and the opposite extremity is the 
posterior end. 
IV. — We have noticed that the entire shell is divided 
equally into two parts, or valves. It is for this reason 
that the term Bivalve was given to the class to which 
the clam belongs. Find a strong, hard hinge or liga- 
ment near the umbones that joins the valves. 

V. — With some sharp instrument carefully force the 

ventral edges of the shell apart, putting some object in 
the space to hold them in position. Then pushing 
aside the ruffled edge of a membrane, insert the knife 
edge close under the valve and carefully push away the 
soft membrane clinging to its inner surface. 

VI. — ; By forcing open the valves a little farther, you will 
be able to see near each end a hard, smooth, white pil- 
lar of muscle fastened to the inner side of the valve. 
These pass directly through the body, and are attached 
in similar positions to the opposite valve. Carefully cut 
out these muscles close to the valve. The springing 
open of the latter shows why the muscles are called the 
adductors. Without disturbing any of the parts, force 
the two valves together, and notice the spring ex- 
erted by the ligament, or hinge. Remember to study 
the mechanism causing this action after the soft parts 
have been removed, or on other shells. 

VII. — Study the concentric rings radiating from the 
umbones. These are the growth lines of the shell as 
it was gradually secreted by the soft membrane first 
seen when the valves were opened. 



Branch Mollusca 79 

INTERNAL ANATOMY 

VIII. — The shell is a true exoskeleton, and its removal 
does not expose the interior or body cavity of the clam. 
On account of the size of the animal and its lateral 
compression, we can do no more than indicate the rela- 
tions of the body cavity and alimentary canal. 

IX. — The membrane above mentioned as found closely 
adhering to the inner side of the shell is the mantle. 
This has two lobes, corresponding in shape to the valves 
of the shell. Demonstrate this fact. Lift the upper- 
most lobe carefully to determine its place of attachment. 
It is simply an outgrowth of the body wall. At the pos- 
terior end find two well-defined oval openings, formed 
by the two mantle lobes coming together. These two 
openings together form the siphon. In the salt-water 
clam the two lobes of the mantle have developed into 
a siphon that extends outward, sometimes an inch or 
more beyond the shell : a black, hard, elongated pro- 
jection, through which these openings pass as wholly 
closed tubes. Water containing food material passes 
in at the ventral or lower opening, and out from 
the dorsal opening. It may be necessary to remind 
the student that we are still talking about the posterior 
end of the animal, and that we have not yet penetrated 
its body wall. 

X. — By raising the mantle lobe examine the exposed, 

hard, white, muscular foot. This is also an extension 
of the body wall, and within its base (the visceral mass) 
are embedded the long coils of the stomach region of 
the alimentary canal. 
XI. — On either side of and posterior to the abdomen find 
the gills, a pair of ribbed membranous organs. Just 



80 Laboratory Guide in Zoology 

anterior to the foot, and below the anterior adductor 
muscle, search for the mouth, a small opening, some- 
times difficult to find. Force a bristle into this up to 
the stomach coils. 

XII. — Attached to the walls of the body, and on each side 
of the mouth find a pair of soft triangular flaps, the 
labial palpi. 

XIII. — Gently detach the body of the clam from the shell 
close under the hinge. Where the two mantle lobes 
unite to form the dorsal body wall, the latter is so thin 
that you may look through it into the body cavity and 
see the straight intestine passing from end to end. Try 
to see the pulsing, colorless, ventricle of the heart, 
through which the intestine passes, though the cavities 
of the two have no connection. With pincers and 
sharp-pointed scissors carefully lift and cut the body 
wall so that the boundaries of the body cavity and its 
organs may be more easily seen. 

XIV. — Trace the intestine forward toward the mouth. 
Examine the dark brown mass surrounding the coils of 
the stomach. This is the liver (very evident in stews 
of the edible clam). As is the usual function of that 
organ, it secretes a digestive fluid that passes into the 
interior of the alimentary canal. 

XV. — Trace the intestine backward, and notice that it 
ends in a space into which the dorsal opening of the 
siphon opens. This space is called the cloacal chamber. 

XVI. — Determine the course taken by the water that 
passes in at the ventral opening. Notice that it bathes 
the gills, the lower part of the body wall and foot, and 
the inner side of the mantle lobes ; then it passes for- 
ward to the labial palpi and the mouth. The cilia which 
cover the labial palpi keep up a constant vibratory 



Branch Mollusca 81 

motion, causing currents in the water to pass into the 
mouth, so that the food in such currents may be taken 
by the clam. The gill chamber is the large cavity in 
which the gills are suspended : it is bounded mainly 
by the mantle. The lower end of the siphon opens 
into it. 

XVII. — It was stated above that currents of water enter- 
ing the lower opening of the siphon escape through 
the dorsal. To make this evident and to demonstrate 
the relation between the cloacal and the gill chambers 
hunt for small openings in the floor of the former. 
Water passes through these from the gills into the 
cloacal chamber and thence out. 

XVIII. — The Nervous System may be very difficult to 
make out in a fresh specimen. Better results are likely 
to be obtained by hardening the specimen in alcohol. 
Remove the mussel entirely from the shell, and with 
the needles search in the median ventral line between 
the gills and directly under the posterior adductor 
muscles for a pair of yellowish masses, or ganglia. Still 
another pair of these nerve centres may generally be 
seen, lying near the surface, one on each side of the 
mouth, close to the bases of the labial palpi. The pedal 
ganglion may be found in front of the intestine in the 
foot. These nerve centres are connected by nerve 
threads called connectives. Trace out as much of the 
connecting system as possible. 

XIX. — The Reproductive Organs will not be easy to study. 
They lie in the abdomen, below and behind the liver. 
They open by ducts into the gill chamber. 

XX. — Make two drawings of the clam : a side view of 
the shell, and a diagrammatic view of the internal 
structure. 



82 Laboratory Guide in Zoology 



THE FRESH-WATER SNAIL 



I 



Fresh-water snails may be easily found at almost any 
season of the year. In summer they are abundant on the 
vegetation in ponds and slow-running streams, while in 
winter they may be easily procured by scraping the bottom 
of the pond with a collecting net. This is especially feasi- 
ble in springs that do not freeze over. This outline is for 
one of the species with conical, pointed shells. Have one 
or more specimens in the hand, and one or more live ones 
in a beaker aquarium. 

I. — Study the specimen as a whole. Notice the three dis- 

tinctive characters of the molluscs, — the foot, the mantle, 
and the shell secreted by the mantle. Make a drawing 
of a side view of one with its body and tentacles 
extended. 

II. — Study the shell. Can the animal part with it? 
Notice the pointed end : this is the apex. Notice the 
open end : this is the aperture. Notice the spiral 
groove : this is the suture. Notice the divisions of the 
shell made by the suture : these are the whorls ; the 
large anterior one is the body whorl, while the others 
together form the spire. The axis from the centre of 
the aperture to the apex is the columella. Notice lines 
around the shell parallel to the lip : these are the lines 
of growth. 

III. — Hold the shell with the apex toward you: if the 
suture turns to the right, the spire is a right-hand or 
dextral spire ; if it turns to the left, it is a left-hand or 
sinistral spire. Or hold the shell with the aperture 
toward you : if the aperture is to the right, the shell is 
dextral ; if to the left, it is sinistral. Which is your 
specimen ? 



Branch Mollusca 83 

IV. — Study the locomotion of the living snail : how is it 
effected ? Can the snail move in any direction in the 
water or on a damp surface outside ? How does the 
large foot on which it moves differ from that of the 
clam ? Can you detect any motion of the different 
parts of the foot while the snail is moving ? 

V. — Where are the tentacles ? How many are there ? 

Can you see a small spot at the base or the tip of the 
tentacles ? These spots are the eyes. 

VI. — As the snail crawls up the wall of the aquarium or 
along the surface film of the water, you can see the 
mouth. Is it longitudinal or transverse as compared 
with the direction of the body ? Describe it's move- 
ment in opening and closing. When it is open, can you 
see a black object moving back and forth ? This is the 
tongue. When magnified this tongue is seen to be 
jagged in outline. 

VII. — Do snails in the water come to the surface occa- 
sionally ? If they do, can you see a bubble of air escap- 
ing from an opening in the mantle of each under the 
lip of the shell? This is the opening to the curious 
lung these snails have. 

VIII. — The eggs of snails may be frequently found on the 
sides of the aquarium. They appear as small granules 
imbedded in a gelatinous mass. Examine some of 
them through a lens. 

IX. — Make a drawing of a side view of the snail and its 
shell. 

THE SQUID 

The squid is a marine mollusc which is frequently 
caught by fishermen in their nets. 

I. — Study the animal as a whole. What characters should 
you say ally it to the class Mollusca ? Notice the long 



84 Laboratory Guide in Zoology 

cylindrical body, covered by a mantle and tapering to 
a point. See the distinct, slightly movable head. Find 
the large eyes, the arms or tentacles, and the mouth be- 
tween the bases of the arms. Find a fold in the mem- 
brane directly back of each of the eyes : these are the 
olfactory lobes. See the opening in the siphon tube 
back of the head on the lower side of the body, and 
the wide terminal fins toward the posterior end of 
the body. 

II. — Study the tentacles. How many are there? How 
do they vary in size ? Notice the two rows of suckers 
on the inner margin of the tentacles : how are they 
arranged ? Of what especial use are the suckers ? 
The pair of long arms are called the grasping arms : 
what is their shape ? What is the arrangement of the 
suckers upon them ? 

III. — Study the mouth. What is its shape? Notice the 
peristome. Open the mouth and notice the large chitin- 
ous jaws. Which is the larger ? The mouth is sur- 
rounded by projections of the skin : how many and of 
what use are they ? 

IV. — Study the large eyes. Is their position an advan- 
tageous one ? 

V. — Study the siphon tube, beneath the head and pro- 

jecting from between the mantle and the neck. Study 
the structure of the orifice. 
VI. — The body is enclosed in a mantle. From what do 
the large terminal fins on the posterior third of the 
body arise ? These fins are used for swimming. 
Around the neck you will find a cavity. This is the 
external part of the mantle cavity. A small projection 
of the mantle over the middle of the head is the pen. 
The squid can take water into the mantle cavity 



Branch Mollusca 85 

and forcibly expel it through the siphon tube, and 
this enables it to dart through the water with great 
rapidity. 
VII. — Make a drawing of the ventral view of the squid. 

THE CLASSIFICATION OF THE MOLLUSCA 

The Mollusca is the great branch, or phylum, to which 
belong the mussels, snails, limpets, and cuttlefishes. Many 
of its members are believed to be closely allied to worms, 
though the members of the two branches differ widely in 
external appearance. In the development of the Mollusca 
the segments have been fused together, while the skin has 
secreted a calcareous shell ; the relative length of the body 
has decreased, and in the lower groups there is no distinct 
head. The alimentary system is greatly developed, espe- 
cially the liver. The phylum includes terrestrial, fresh- 
water, and marine forms. There are three principal 
classes : — 

I. — Pelecypoda. Oysters and Clams. 

This class includes " laterally compressed Mollusca 
without separated head, with bilobed mantle and bi- 
valve shell, composed of a right and left half and con- 
nected by a dorsally placed ligament." The sexes are 
generally separate, and there are large gill-plates on 
account of which the class has commonly been called 
Lamellibranchiata. The locomotive organ consists of 
a single median muscular foot, and the parts of the 
body are arranged with bilateral symmetry. Both 
salt and fresh water forms are included, all of which 
breathe by means of gills. 

II. — Gastropoda. Snails, Slugs, and Limpets. 

The members of this class usually have a shell in a 
single piece which commonly has the shape of a spiral 



86 Laboratory Guide in Zoology 

cone. The body is not symmetrical, and in front of 
the foot there is a head which bears the tentacles and 
eyes. These animals are widely distributed : the 
largest number live in salt water, but many live in fresh 
water, and many are terrestrial. Some breathe by 
means of gills ; others by means of lungs. 
III. — Cephalopoda. Cuttlefishes and Squids. 

This class includes the highest molluscs, the most 
important examples being the Cuttlefish, Squid, Octo- 
pus, and Nautilus. The members of it are bilaterally 
symmetrical with the head separated from the body by 
a slight constriction. There are two well-developed 
eyes, a rasping tongue, a beak, and eight or more 
tentacles. The ganglia of the head are somewhat pro- 
tected by a covering. 



CHAPTER IX - 
BRANCH CHORDATA: THE VERTEBRATES 

THE PERCH 
EXTERNAL ANATOMY 

I. — General Form. Study the graceful outline of the fish 

from a side view. From a dorsal view, see how the 
body is compressed laterally. Observe how the head, 
although flattened at the tip, passes with graceful 
curves into the body. Account for the compressed 
body, flattened head, and the absence of a neck by refer- 
ence to the animal's habitat and locomotion. Notice 
the absence of any segmented division of the body axis. 
Segmented structures will be found to exist, however, 
when we study the skeleton and muscles. Study the 
coloration of the fish. Account for its dark dorsal and 
light ventral surface by reference to its needs of self- 
protection. Notice the alternating perpendicular bands 
of black and white along the sides. Explain how this 
arrangement of color also makes the fish less conspicu- 
ous in its natural haunts. 

II. — Exoskeleton. Study the scales of the perch. Re- 
move some of them, and with the low power of the 
microscope see the thin covering. Draw one. The 
scales themselves are the outgrowths of the inner or 
true skin, while their covering corresponds to the outer 
skin or epidermis of the higher animals. 

87 



88 Laboratory Guide in Zoology 

III. — Appendages. Study the two fins running along the 
dorsal median line. They are made up of a web sup- 
ported by hard spines. How do the spines in the two 
fins differ? The tail is called the caudal fin. What 
kind of rays has it ? When the caudal fin is symmetri- 
cal, it is said to be homocercal; when it is bent so that it*, 
is unsymmetrical, it is said to be heterocercal. Which is 
the case in the perch ? On the mid-ventral side of the 
body, just in front of the caudal fin, find the anal fin. 
Note the fact that all fins studied above are median or 
single, i.e. never in pairs. Next observe a pair of fins 
(pectoral) just back of the head, one on each side of the 
body. They correspond to and indeed are homologous 
with the fore legs or arms of the higher animals. Back 
of the pectoral fins, and nearly on the ventral line, find 
the pair of pelvic fins, corresponding to the hind legs of 
the higher animals. Take a general view of the fins 
with reference to their uses. Tell which keep the ani- 
mal in an upright position, and which give it propelling 
power and guidance. 

IV. — Other Organs. Study the action of the jaws, noticing 
that both have movement. Is the action up and down 
or from side to side ? Place a finger in the mouth to 
feel the teeth, noticing their slanting direction. Study 
the size and position of the eyes. Find with the for- 
ceps the bony socket encasing the eyes. Move the 
eye itself to find its field of vision. Are there any 
eyelids ? Find the nasal opening in the upper lip. 
Find the anal opening just in front of the anal fin. 

V. — Breathing Apparatus. Find a large, slit-like opening 

on each side of the head just back of the mouth which 
communicates directly with the mouth cavity. These 
are the gill-chambers, and the flaps closing over them 



Branch Chordata 89 

are the gill-covers. The gill-arches are the four bony 
arches standing side by side within the gill-chambers. 
Attached to the gill-arches are the red filamentous 
structures, the gills. Are the gill-chambers in direct 
communication with the exterior from both sides ; if so, 
are the gills constantly bathed in water ? As the blood 
passes through the many filaments of the gills, oppor- 
tunity is given for it to exchange its carbonic acid for 
the oxygen of the water. 

INTERNAL ANATOMY 

VI. — Body Cavities. Insert the point of the scissors just 
in front of the anal opening, and cut through the body 
wall to the gill-slits. Push the flaps aside, and observe 
the main body cavity. Notice how the cavity with its 
organs is crowded forward, leaving the posterior parts 
for the strong muscles. Notice the shining membra- 
nous lining, the peritoneum. Near the anterior end of 
the body cavity you may find a membranous partial 
partition corresponding to the diaphragm of the higher 
vertebrates. 

VII. — Blood System. Near the middle of the smaller 
anterior cavity a dark reddish body, the heart, will be 
found. There are but two cavities in the heart, — the 
rather angular, thick-walled ventricle and the dark, irreg- 
ular auricle. You may be able to find connected with 
the auricle a dark, thin-walled vessel, the venous sinus, 
extending across the body cavity. The venous sinus 
receives the blood from the veins, and passes it on to the 
auricle. Find and trace as many vessels as you can 
connected with the heart or venous sinus. 

VIII. — Digestive System. Pass a blunt instrument down 



90 Laboratory Guide in Zoology 






the oesophagus to observe its union with the stomach. 
Then follow the intestine from the stomach in its not 
long course to the anal opening. The large, reddish 
lobed object lying in the anterior part of the body cavity 
is the liver. Try to make out its connection with the 
intestine. The gall-bladder is a small, greenish body, 
partly concealed by and closely connected with the 
liver. 

IX. — Reproductive and Excretory Organs. In the vertebrates, 
as in many invertebrates, the sexes are separate. So in 
the fish we must look for testes or ovaries, never both. 
The appearance of the female organs or ovaries varies 
greatly with the season. In spawning time the ovaries 
may be so distended that they cover all the other organs. 
At other times they have the appearance of a single 
white body lying near the intestine. A delicate tube leads 
from this to an opening toward the posterior end of the 
body. If the specimen is a male, the testes will be 
found to be a pair of white bodies lying in the posterior 
dorsal part of the abdominal cavity. Ducts may be 
found passing to an opening toward the posterior end 
of the body. After clearing away the intestine and 
reproductive organs, a broad, flat, membranous sac may 
be seen, if it has not already been punctured : this is 
the air-bladder ; it is connected with the oesophagus. 
Its function is to decrease the specific gravity of the fish 
by filling it with air. Remove the air-bladder, and find 
two long, dark, slender bodies, the kidneys. Trace their 
ducts to the outlet near the anal opening. Near the 
outlet a pinkish sac, the urinary bladder, will be found. 

X. — Endoskeleton and Central Nervous System. Cut the 

flesh away from the dorsal surface of the fish, expos- 
ing the backbone as completely as possible. Notice 



Branch Chordata 91 

that this flesh is composed of muscle segments or 
myotomes. Observe the jointed or segmented nature 
of the backbone or spinal column. Its lateral bony 
processes are analogous to the ribs of the higher verte- ^ 

brates. Each separate segment is a vertebra. Passing 
along a closed tube within the spinal column is the 
spinal cord, ending anteriorly in the brain. The two 
(spinal cord and brain) constitute the central nervous 
system. Nerves pass from this through openings 
between the vertebrae to various parts of the body. 
Break the connection between two of the vertebrae to 
see the cavity filled by the spinal cord. Open the 
cranium, or brain case, by removing carefully the dorsal 
surface of the head just back of the eyes. Study the 
lobes of the brain now exposed. Follow the continua- 
tion of the brain into the spinal cord. Without injuring 
the lobes of the brain, carefully dissect away sufficient 
surrounding tissue to see the. large optic nerves passing 
to the eyes. If the lobes of the brain still remain com- 
plete and uninjured, follow out the different parts. 
The small median lobe extending backward is the 
cerebellum. The pair of large rounded lobes directly 
in front of the cerebellum, constituting the broadest 
part of the brain, are the optic lobes. The cerebral 
lobes, or hemispheres, are much smaller, and lie directly 
in front of the optic lobes nearly on the median line. 
The somewhat flattened posterior part of the brain, 
passing from the cerebellum into the spinal cord, is 
the medulla oblongata. Make a drawing of the brain. 



92 Laboratory Guide in Zoology 

THE FROG 
EXTERNAL ANATOMY 

I. — General. Feel of the frog's skin, noting its smooth, slimy 

nature. The moisture is a secretion from the glands 
in the skin. Note the general temperature of the body. 
It is cold even in life. Study the color markings of the 
dorsal and ventral surfaces, and give reasons for such 
coloring. The frog has the power to change its color, 
bringing it into closer harmony with its surroundings. 
The frog is placed in the group of animals called Am- 
phibia. All Amphibians belong to the larger group 
called Vertebrata. Fishes, reptiles, birds, and mam- 
mals, besides Amphibians, are vertebrates. Fishes and 
reptiles, like Amphibians, are cold blooded. Notice 
that the frog has no outer skeleton. Note the absence 
of an external division of the body axis. 

A segmented condition will be found to exist, how- 
ever, when we study the skeleton. Examine the limbs 
with special reference to the animal's habit of locomo- 
tion. Is the animal well adapted to its environment 
in this respect ? Remember that the number of limbs 
possessed by the frog is the maximum for verte- 
brates. 

II. — External Openings. Examine the nature and position 
of the mouth and cloacal opening. Study the position 
of the eyes with reference to their field of vision and 
protection. In the anterior parts of the upper jaw find 
two small openings into the nasal cavities. Push the for- 
ceps or some blunt instruments through them into the 
mouth. Behind each eye find a circular disk of tightly 
stretched membrane, the external apparatus of the ear. 






Branch Chordata 93 

Inside the mouth at the back find the eustachian tube, 
a passage leading to the drum of the ear. 

INTERNAL ANATOMY 

III. — Dissection. With scissors or sharp scalpel cut the 
skin from the edge of the lower jaw along the median 
ventral line to the cloacal opening. Notice how loosely 
the skin is attached to the body. Where is the prin- 
cipal place of attachment? Make lateral slits in the 
skin and pull away the flaps, pinning them if necessary. 
Remove the skin from the legs in the same manner. 
Observe the development of the powerful chest muscles ; 
also the muscles in the hind legs used as the propelling 
power in long leaps. Next, cut the body wall from end 
to end, in a similar manner to the incision of the skin, 
being very careful not to disturb any of the viscera 
beneath. Make lateral slits and pin back the flaps of 
the body wall, exposing the internal organs. A circlet 
of bones to which the legs are attached passes over the 
chest just above the heart. Cut these with strong 
scissors. 

IV. — General. Recalling the general plan on which the 
earthworm and lobster are built, you w T ill remember 
that it is a tube within a tube. The wall of the outer 
tube, being the body wall, encloses the body cavity ; 
while the inner tube is the alimentary canal, with its 
two openings. Find a similar structure now revealed 
in the case of the frog. The large cavity holding the 
various organs, or viscera, is the body cavity, or outer 
tube, and through this passes the alimentary canal, or 
inner tube. The latter is now partly visible as the 
light-colored stomach or intestine. 



94 Laboratory Guide in Zoology 

V. — Blood System. Just beneath the position of the 
chest bones the heart may be seen. It is a cone-shaped 
body, darker at the apex. There are only three cham- 
bers, — one ventricle and two auricles. The ventricle 
forms the apex of the cone and has walls much thicker 
than those of the auricles. Give reasons for this. 
Notice that there is no blood fluid in the body cavity. 
The blood circulates in a closed system, passing from 
the heart in arteries and returning in veins, instead of 
being left to find its way back to the heart by con- 
tractions of the body. Observe the large vessels leaving 
the heart ; the arteries cannot be easily distinguished 
from the veins. Follow the vessels as far as you can 
without disturbing the other organs. 

VI. — Digestive System. Without removing the viscera, 
study the entire alimentary tube and its appendages, 
with the aid of the following directions : Move the jaws 
up and down. Do they move in the same direction as 
the jaws of insects or crustaceans move? Notice the 
attachment of the tongue at its anterior end. The 
posterior end is moistened by a sticky secretion from 
the roof of the mouth, and protruded for the prehen- 
sion of food. The mouth opens into the oesophagus, 
and thence into the stomach — the elongated, thick- 
walled enlargement of the tube. Pass some blunt 
instrument down the oesophagus, or inflate with a 
tube to observe the relation of the mouth, oesophagus, 
and stomach. From the stomach follow out the small 
intestine, large intestine, and cloaca, the last enlarge- 
ment. Into the cloaca pass the contents of the repro- 
ductive organs. 

VII. — Appendages of the Tube. Find the liver, a dark- 
lobed, very conspicuous body, lying near the heart. 



Branch Chordata 95 

Partly concealed by the lobes of the liver, find a small, 
spherical, dark green body, the gall-bladder. Is it con- 
nected with the liver and intestine ? Find somewhat 
closely connected with this a long, irregular, pink- 
colored body, the pancreas. Trace out the ducts of the 
pancreas, gall-bladder, and liver as well as possible. 
The red spleen is farther back in the abdominal cavity. 

VIII. — Respiratory System. Find the dark, thin-walled, 
inflated bodies, the lungs, one on each side of the 
heart. Through their walls runs a network of blood- 
vessels, thus bringing the blood into close connection 
with the air filling the lungs. In the floor of the 
mouth, just back of the tongue, find the slit-like open- 
ing of the larynx, a chamber which connects with the 
lungs. Pass something down the larynx to see the 
relation to the lungs. 

IX. — Reproductive System. The frog, like all vertebrates, 
and many invertebrates, is unisexual, i.e. an individual 
possesses but one kind of sexual organs. If the speci- 
men is a female, large, irregular bodies, the ovaries, 
will be found on each side of the posterior part of the 
abdomen. Within these are found the cells which 
develop into eggs. During the breeding season the 
eggs pass from the ovary into the body cavity, and 
from there to the exterior by oviducts. These are 
coiled, tubular organs, with a funnel-shaped opening, 
and they pass to the cloaca. The openings of the ovi- 
ducts possess small cilia, whose vibrations guide the 
eggs into them, and as the eggs pass through they 
gather a mucus secreted by the walls of the duct. 
This mucus swells greatly on striking the water, and 
we may thus account for the appearance of the frog's 
eggs when seen in ponds. 



96 Laboratory Guide in Zoology 

X. — If the specimen is a male, two small, oblong, light- 
colored bodies, the testes, will be found, one on each 
side of the median line just anterior to the cloaca. 
They produce sperm cells that pass directly by minute 
tubes into the kidney and thence by the ureter to the 
cloaca and to the exterior, where they fertilize the eggs 
from the female. 

XL — Excretory Organs. Excretory organs are used to 
throw off the waste material of the body. Hence the 
lungs, kidneys, and skin may be grouped together as 
parts of the excretory system. We have here only to 
study the kidneys. These are two flat, oblong bodies, 
lying one on each side of the median line in front of 
the cloaca and dorsal to the testes. As the blood passes 
through the walls of these bodies, it is relieved of certain 
waste materials that pass through ducts, the ureters, into 
the cloaca by openings in its dorsal wall. The bladder 
is a colorless bag which opens into the ventral side 
of the cloaca. Find the ureters. 

XII. — Skeleton. Cut away the viscera already studied, 
leaving the backbone, or spinal column, exposed on its 
ventral side. Cut away the muscles on the fore and 
hind legs without severing the ligaments that bind the 
bones. Notice that in its general plan the skeleton 
is made up of a central axis (spinal column) and its 
appendages (limbs, etc.). Notice the segmented char- 
acter of the backbone. Each segment is a vertebra. 
The unsegmented posterior part of the axis represents 
the fused segments that form the tail in other verte- 
brates. 

XIII. — Nervous System. This may be divided into two 
great divisions, — the cerebrospinal and the sympathetic. 
The cerebrospinal system is made up of the brain and 



Branch Chordata 97 

the spinal cord, and is now wholly invisible within the 
cranium and the spinal column. The sympathetic sys- 
tem may be seen in the shape of white cords lying 
on the dorsal floor of the body wall on each side of the 
spinal column. It is connected with the cerebrospinal 
system by branches between the vertebrae. The func- 
tion of the cerebrospinal system is to govern the 
action of the muscles attached to the skeleton (skele- 
tal muscles), while the sympathetic system controls 
the action of the visceral organs. By bending, sever the 
connection between the vertebrae, in order to see the 
spinal cord lying in a cavity within the solid bone of 
the spinal column. Carefully remove the bone from 
the dorsal surface of the cranium to see how the spinal 
cord terminates in the brain. 

The position of the central nervous system (cerebro- 
spinal) lying in a tube parallel to and wholly separated 
from the main tube (body cavity), and on the dorsal 
side of the body is an important characteristic of verte- 
brates as distinguished from invertebrates. 

XIV. — Study again the pectoral arch, — the circlet of 
bones supporting the forward legs. It corresponds 
to our collar bone and shoulder blade. 

XV. — Study the pelvic arch — the bones supporting the 
hind legs. Study the bones of the fore and hind limbs, 
noticing the similarity between the two pairs in the ar- 
rangement of the bones. Make comparisons between 
the bones of the limbs of the frog and those of the 
higher vertebrates by aid of the following outline : — 

In the fore legs, beginning with the segments next to 
the body, the names and homologies are : {a) humerus, 
which corresponds to the upper arm in man ; (b) ulno- 
radius, which corresponds to the ulna and radius of our 



98 Laboratory Guide in Zoology 

forearm united ; (c) the small bones following, gener- 
ally six, correspond to the bones of the wrist and may 
be called the carpus ; {d) next to the carpus there are 
five bones, corresponding to the bones of the palm of 
the hand (one is much smaller than the others and 
corresponds to the thumb) and all together compose 
the metacarpus ; (<r) the remaining bones making the 
four fingers are called the phalanges. 
XVI. — In a similar manner follow out the bones in the 
hind legs : (a) the femur corresponds to the thigh bone; 
(J?) the tibio-fibula corresponds to the shank ; (c) the 
tarsus corresponds to the bones of the ankle ; (d) the 
metatarsus corresponds to the bones of the foot ; and 
(e) the phalanges correspond to the bones of the toes. 

THE BIRD 

The English sparrow will serve very well for the follow- 
ing study of the structure of a bird. 

EXTERNAL ANATOMY 

I. — General. Study the general structure of the body, 

noting that it may be easily divided into head, neck, 
trunk, and tail. In the trunk find the thoracic and the 
abdominal regions. In what ways does the bird differ 
from the frog ? 

II. — Observe the hard beak composed of two mandibles. 
Which of these is movable ? Find the tongue, extend- 
ing it with a pair of forceps. Describe its surface 
above and below. Are there any projections upon it? 
Of what use might they be ? Behind the hard part of 
the tongue find an opening — the glottis. 

III. — Study the inner surfaces of the jaws. Find what 



Branch Chordata 99 

appears to be a longitudinal opening in the roof of the 
back part of the mouth. Push a pin through the 
nostrils from the outside. Where does its point enter 
the mouth ? 

IV. — Study the eyes and eyelids. How are the latter 
attached ? See if you can find the nictitating mem- 
brane which sometimes covers the eye of the living 
bird. 

V. — Study the ear-opening. Describe its size and shape. 
VI. — Study the wings. How does their length compare 

with that of the body ? How many joints in them ? 

VII. — Observe the kinds of feathers and their distribu- 
tion over the body. Do you find on the trunk any 
feather tracts beside comparatively bare places ? Take 
a long feather from wing or tail : see its central stem 
or axis, and the vane which is made up of a vast num- 
ber of barbs which in turn branch into barbules. The 
barbules hold the barbs together. Are they more 
effective toward the basal or the apical end of the 
feather ? Compare a feather from the ear and one from 
the breast with the long one. How do they differ ? 

VIII. — Study the legs : what bones should you think are 
covered by the feathers ? Is there any system in the 
arrangement of the scales on the tarsus and toes ? 
Notice the shape of the claws on the toes, and the pro- 
tection along the under surface of the toes. 

INTERNAL ANATOMY 

IX. — Lay the specimen on its back in the dissecting 
dish with its head pointing toward you. Cut the skin 
along the median ventral line, beginning at the pos- 
terior extremity of the lower mandible. Pushing back 

LofC. 



ioo Laboratory Guide in Zoology 

the cut skin, notice over the thorax the large and 
powerful pectoral muscles which control the movement 
of the wings. Which way do the muscle fibres 
extend ? 

X. — Circulatory System. Cut through the pectoral mus- 

cles and soft breastbone (sternum), extending the 
incision back through the abdominal walls, thus expos- 
ing the viscera of the thorax and abdomen. In the 
thorax see the heart. Lift it carefully and cut the 
connective tissues in such a way as to enable you to 
study the important blood-vessels. From the front 
of the heart on the left see the large aorta which 
comes from the left ventricle. Before turning back- 
ward this gives off the innominate arteries — one to 
the right and one to the left. Each innominate artery 
in turn has three branches ; namely, a carotid, extend- 
ing forward toward the head ; a brachial, extending to 
the wings, and a pectoral, extending to the pectoral 
muscles. The large aorta extending backward may be 
studied a little later when the thoracic and abdominal 
viscera are removed. On its course it gives off various 
branches, — to the stomach, to the liver, and to the legs. 
Find three good-sized veins which pass into the right 
auricle, and the right and left pulmonary arteries 
which go from the right ventricle to the lungs. 

XI. — Study the structure of the heart itself. By cutting 
transversely across the lower end see whether the ven- 
tricles are completely separated from each other. Now 
make a longitudinal section and study the structure of 
the valves that connect one chamber with another. 

XII. — Mount a drop of blood upon a glass slide, and 
study the shape of the corpuscles as seen with a high 
power of the microscope. Make drawings of them. 



Branch Chordata 101 

XIII. — Digestive System. Study the alimentary canal. 
Beginning at the mouth see the straight tube, the 
oesophagus, extending backward to the enlarged crop, 
and then continuing to the muscular walled gizzard. 
Open this : what is inside ? What is the chief use of 
the gizzard ? Back of the gizzard see that the alimen- 
tary tube continues as the duodenum, more or less curved 
and looped. Within this loop see the pancreas — a 
yellowish gland. Lift the pancreas and find where its 
ducts enter the duodenum. At this time study also the 
liver with its two large lobes, and find the greenish 
gall-bladder between them. Directly under the gizzard 
see the small, flattened, red spleen. The alimentary tube 
continues backward from the duodenum as the small 
intestine, much convoluted, until it enlarges in the 
cloaca near the posterior end. Notice the coeca on the 
small intestine. Make a sketch of the alimentary tube 
and its connections. 

XIV. — Respiratory System. The cartilaginous trachea is 
easily seen extending from the mouth to the thoracic 
cavity, where it divides into the bronchi, one passing to 
each lung. Inflate the lungs through a tube inserted 
into the trachea through the glottis, where it opens into 
the mouth. 

XV. — Reproductive System. If your specimen is a male, 
the oval glandular testes will be readily seen in the 
abdominal cavity after the alimentary system is re- 
moved. Find a convoluted vas deferens running from 
each to the cloaca. If your specimen is a female, you 
will see the glandular ovary. A single oviduct on the 
left side of the body opens into the cloaca. Only a 
vestige of the right oviduct remains. 

XVI. — Renal System. When all the abdominal viscera 



102 Laboratory Guide in Zoology 

are removed, the kidneys are to be seen as dark-colored, 
flattened bodies, fitting closely against the bones of the 
back, one on each side the spinal column. Find a 
tubular ureter running from each kidney to the cloaca. 
XVII. — Nervous System. If the head is cut off and placed 
in alcohol for a day or two, the brain will be hardened 
so it can more readily be studied. Remove the upper 
part of the skull by cutting with strong scissors from 
the beak over the eyes and around the back of the 
head, thus exposing the brain. Note these parts of it : 
the large cerebral hemispheres with the elongated 
cerebellum immediately behind on the dorsal side ; the 
two olfactory lobes beneath the front part of the cerebral 
hemispheres, and the two optic lobes in front of and at 
the sides of the cerebellum. Make a drawing showing 
the parts of the brain as seen from above and another 
as seen from the side. 



THE CLASSIFICATION OF THE VERTEBRATES 

The highest branch in the animal kingdom is called 
the Chordata. " It comprises all the Vertebrate Animals 
(Fishes, Amphibians, Reptiles, Birds, and Mammals), 
together with the Urochorda, or Ascidians, and the Adelo- 
chorda, or Balanoglossus, and its allies. The name Chor- 
data is derived from one of the most important of the few 
common features by which the members of this extensive 
phylum are united together — the possession either in the 
young condition or throughout life of a structure termed 
the chorda dorsalis, or notochord. This is a chord of cells, 
typically developed from the endoderm, extending along 
the mid-dorsal line above the enteric tube on the ventral 
side of the central nervous system. It becomes enclosed 



Branch Chordata 103 

in a firm sheath, and forms an elastic supporting structure. 
In the Vertebrata (with the exception of Amphioxus and 
the Lampreys and Hagfishes) it becomes in the adult 
replaced more or less completely by a segmented bony 
or cartilaginous axis — the spinal or vertebral column." 
(Parker and Haswell.) 

The branch or phylum Chordata is divided into three 
subbranches or subphyla, namely : — 

Subphylum I. Adelochorda. Balanoglossus. 

Subphylum II. Urochorda. Ascidians and Sea-squirts. 

Subphylum III. Vertebrata. Fishes, Amphibians, Rep- 
tiles, Birds, and Mammals. 

The first of these includes the remarkable worm-like 
animals belonging to the genus Balanoglossus. The 
second comprises the Ascidians or Sea-squirts, which are 
often called Tunicates and grouped together under the 
name Tunicata. The third includes the vertebrates proper, 
in which are found the highest animals. 

In the subphylum Vertebrata, some of the very lowest 
fish-like forms have no skull, or development of the ante- 
rior end of the vertebral axis. These are classed under 
the head of Acrania. All the others, or those with a skull, 
are called Craniata. These are divided into six great 
classes, named below in the order of their natural develop- 
ment. The first four are cold blooded, and the other two 
are warm blooded. 

Class I. Cyclostomata. Lampreys. 

This class comprises comparatively few forms, which 
have in place of jaws a suctorial mouth; they have no 
fins or other lateral appendages, and only one nasal 
aperture. The Lampreys and Hagfishes belong to this 
class. 

Class II. Pisces. Fishes. 



104 Laboratory Guide in Zoology 

The members of this and the preceding classes are the 
lowest of the true vertebrates, not only in structure, but 
also in strength, intelligence, and sensibility. As a class, 
however, the fishes are superior to all the others in number 
and variety of forms. They live always in the water, are 
cold blooded, and breathe by gills. Their fins are homolo- 
gous with the limbs of the higher vertebrates. 

Class III. Amphibia. 

The Amphibia are cold-blooded animals, having gills 
when young, and lungs when adult. In the early stages 
the tail is modified into a swimming organ. The eggs are 
deposited in the water or upon moist surfaces, the skin is 
soft and naked, and the skeleton is bony or ossified. 
There is no distinct neck. There are a number of orders 
of Amphibia, the lower including the newts and salaman- 
ders, or the tailed Amphibians, while the higher include 
the frogs and toads. 

Class IV. Reptilia. Reptiles. 

These are cold-blooded animals, distinguished from the 
Amphibia by never having gills, and from birds by the 
absence of feathers. With the exception of some of 
the turtles, they are carnivorous. The Reptilia includes 
the snakes, the lizards, the turtles, and the crocodiles. 

Class V. Aves. Birds. 
This is the most clearly defined class in the animal king- 
dom. Its members are air-breathing, egg-laying, feathered 
vertebrates with the front limbs developed for flying or 
swimming, and the hind limbs for perching, walking, or 
swimming. The bones are light and compact, and the neck 
is usually long. The birds are a group of great interest 
and of the greatest economic importance, whether we con- 
sider their direct value to man as food, or their indirect 
benefits in checking insect and other animal pests. 



Branch Chordata 105 

Class VI. Mammalia. Mammals. 

This is the highest class of the vertebrates. The mam- 
mals furnish milk for their young ; they breathe air by 
means of lungs ; they have a four-chambered heart, and 
a double circulation of the blood ; and the thorax and 
abdomen are separated by a diaphragm. The members 
of this group vary from the curious duck-bill of Australia 
to man. 



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